Langerak, A.W.

Multicolor flowcytometric immunophenotyping is a valuable tool for detection of intraocular lymphoma (Article)

2013-05-01T00:00:00Z

Objective: Intraocular lymphoma (IOL) is a rare condition and frequently difficult to distinguish from uveitis or other uveitis-masquerading syndromes. The diagnosis is confirmed by cytologic examination of ocular fluid specimens and more recently by molecular-immunoglobulin heavy chain (IGH) translocation or cytokine analysis. However, some of these more recent methods have not been validated by follow-up studies. Design: Evaluation of a diagnostic test. Participants: In a cohort of 51 consecutive patients with a clinical suspicion of IOL, vitreous analysis was performed via multicolor flowcytometric immunophenotyping. Methods: Multicolor flowcytometric immunophenotyping was performed with CD45, CD3, CD19, CD20, anti-SmIgκ, and anti-SmIgλ antibodies. The presence of a clear B-cell population showing a disequilibrium of Igκ versus Igλ expression was used to confirm the diagnosis of non-Hodgkin lymphoma (NHL). Patients were followed for a minimum of 2 years (mean, 5.9±2.0 years) to validate the accuracy of the method. Main Outcome Measures: The presence or absence of IOL during follow-up. Results: In 14 of 51 patients, a clinical diagnosis of IOL was confirmed using flowcytometric analysis. Of these 14 patients, 11 had primary IOL and 3 had metastasized secondary lymphomas. In 3 of 51 patients who were diagnosed with (central nervous system) NHL during follow-up, the test failed to confirm the presence of a clonal B-cell population. In 18 of the 34 other patients, an infectious or well-defined immunologic disorder was established during follow-up. The remaining 16 patients, with a minimal follow-up of 2 years, were diagnosed with idiopathic uveitis. Conclusions: Multicolor flowcytometric analysis had 82.4% sensitivity and 100% specificity in patients with suspected IOL. This is comparable to the reported vitreous interleukin (IL)-6/IL-10 testing sensitivity of 0.8 and sensitivity of 0.65 to 0.95 by immunoglobulin heavy chain (IGH) gene arrangement testing in clinical cohorts. Because flowcytometric tests are readily performed in hematologic laboratories, this can be regarded as a useful method for confirming the clinical diagnosis of IOL.

Combined TCRG and TCRA TREC analysis reveals increased peripheral T-lymphocyte but constant intra-thymic proliferative history upon ageing (Article)

2013-03-01T00:00:00Z

T-cell receptor (TCR) repertoire diversity, thymic output, clonal size and peripheral T-lymphocyte numbers largely depend on intra-thymic and post-thymic T-lymphocyte proliferation. However, quantitative insight into thymocyte and T-lymphocyte proliferation is still lacking. We developed a new TCRG-based TCR excision circle (TREC) assay, the Vγ-Jγ TREC assay, which we used together with an adjusted δREC-ψJα TREC assay to quantify the proliferative history of human thymocyte and T-lymphocyte subpopulations from children and adults. This revealed that thymocytes undergo ∼6-8 intra-thymic cell divisions from the double negative (DN) 3 developmental stage onwards, which appeared independent of age. Thus thymocyte proliferation after the DN3 developmental stages is stable and therefore not contributing to the reduced thymic output upon ageing. Cord blood naive T lymphocytes had already undergone ∼2-3 post-thymic cell divisions, which increased to ∼6-7 cell divisions in naive T lymphocytes of middle-aged adults, indicating the importance of homeostatic naive T-lymphocyte proliferation from a young age onwards in the maintenance of peripheral T-lymphocyte numbers. In conclusion, our data provide quantitative insight into the proliferative history of thymocyte and T-lymphocyte subpopulations and alterations herein upon ageing. This novel TREC assay approach could prove valuable in immune status monitoring in a variety of conditions.

A novel chronic lymphocytic leukemia subset expressing mutated IGHV3-7-encoded rheumatoid factor B-cell receptors that are functionally proficient (Article)

2013-03-01T00:00:00Z

The defect in humoral immunity in patients with Nijmegen breakage syndrome is explained by defects in peripheral B lymphocyte maturation (Article)

2012-10-01T00:00:00Z

Patients with an immunodeficiency in the course of Nijmegen breakage syndrome (NBS) that is caused by mutations in the NBN/NBS1 gene are prone to recurrent infections and malignancies, due to a defective DNA double-strand breaks repair mechanism. Four-color flow cytometry was used to analyze changes in B lymphocyte subsets reflecting the most important stages of peripheral B cell maturation. It was demonstrated that the humoral immune defect observed in NBS patients was caused by reduced numbers of B lymphocytes, but also by their aberrant maturation. Reduced relative and absolute counts of naïve and memory B cells were accompanied by a significant accumulation of the natural effector B lymphocytes. The elevated proportion of IgM-only memory and reduced proportion of IgM-negative cells within the memory B cell pool suggests that there is class-switch recombination defect in this population of cells in NBS patients, resulting in inadequate production of immunoglobulins. Because of the reduced T-cell counts, the T-cell dependent antigen response is severely impaired resulting in a lower frequency of memory B-cells. The T-cell independent B-cell differentiation pathway seems less affected. The reduced IgG and IgA levels in patients with NBS are caused both by ineffective class switch, at least due to poor T cell help, and low number of memory B cells. This study illustrates that the NBN gene product nibrin plays an important role at different levels in the B-cell system.

TLX Homeodomain Oncogenes Mediate T Cell Maturation Arrest in T-ALL via Interaction with ETS1 and Suppression of TCRα Gene Expression (Article)

2012-04-17T00:00:00Z

Acute lymphoblastic leukemias (ALLs) are characterized by multistep oncogenic processes leading to cell-differentiation arrest and proliferation. Specific abrogation of maturation blockage constitutes a promising therapeutic option in cancer, which requires precise understanding of the underlying molecular mechanisms. We show that the cortical thymic maturation arrest in T-lineage ALLs that overexpress TLX1 or TLX3 is due to binding of TLX1/TLX3 to ETS1, leading to repression of T cell receptor (TCR) α enhanceosome activity and blocked TCR-Jα rearrangement. TLX1/TLX3 abrogation or enforced TCRαβ expression leads to TCRα rearrangement and apoptosis. Importantly, the autoextinction of clones carrying TCRα-driven TLX1 expression supports TLX "addiction" in TLX-positive leukemias and provides further rationale for targeted therapy based on disruption of TLX1/TLX3.

DNA methylation pattern is altered in childhood T-cell acute lymphoblastic leukemia patients as compared with normal thymic subsets: Insights into CpG island methylator phenotype in T-ALL (Article)

2012-02-01T00:00:00Z

Morbidly obese human subjects have increased peripheral blood CD4 + T cells with skewing toward a Treg- and Th2-dominated phenotype (Article)

2012-02-01T00:00:00Z

Obesity is associated with local T-cell abnormalities in adipose tissue. Systemic obesity-related abnormalities in the peripheral blood T-cell compartment are not well defined. In this study, we investigated the peripheral blood T-cell compartment of morbidly obese and lean subjects. We determined all major T-cell sub-populations via six-color flow cytometry, including CD8+and CD4+T cells, CD4+T-helper (Th) subpopulations, and natural CD4+CD25+FoxP3+T-regulatory (Treg) cells. Moreover, molecular analyses to assess thymic output, T-cell proliferation (T-cell receptor excision circle analysis), and T-cell receptor-β (TCRB) repertoire (GeneScan analysis) were performed. In addition, we determined plasma levels of proinflammatory cytokines and cytokines associated with Th subpopulations and T-cell proliferation. Morbidly obese subjects had a selective increase in peripheral blood CD4+naive, memory, natural CD4+CD25+FoxP3+Treg, and Th2 T cells, whereas CD8+T cells were normal. CD4+and CD8+T-cell proliferation was increased, whereas the TCRB repertoire was not significantly altered. Plasma levels of cytokines CCL5 and IL-7 were elevated. CD4+T-cell numbers correlated positively with fasting insulin levels. The peripheral blood T-cell compartment of morbidly obese subjects is characterized by increased homeostatic T-cell proliferation to which cytokines IL-7 and CCL5, among others, might contribute. This is associated with increased CD4+T cells, with skewing toward a Treg- and Th2-dominated phenotype, suggesting a more anti-inflammatory set point.

Notch induces human T-cell receptor γ δ+ thymocytes to differentiate along a parallel, highly proliferative and bipotent CD4 CD8 double-positive pathway (Article)

2012-01-01T00:00:00Z

In wild-type mice, T-cell receptor (TCR) γδ+cells differentiate along a CD4 CD8 double-negative (DN) pathway whereas TCRαΒ+cells differentiate along the double-positive (DP) pathway. In the human postnatal thymus (PNT), DN, DP and single-positive (SP) TCRγδ+populations are present. Here, the precursor-progeny relationship of the various PNT TCRγδ+populations was studied and the role of the DP TCRγδ+population during T-cell differentiation was elucidated. We demonstrate that human TCRγδ+cells differentiate along two pathways downstream from an immature CD1+DN TCRγδ+precursor: a Notch-independent DN pathway generating mature DN and CD8αα SP TCRγδ+cells, and a Notch-dependent, highly proliferative DP pathway generating immature CD4 SP and subsequently DP TCRγδ+populations. DP TCRγδ+cells are actively rearranging the TCRα locus, and differentiate to TCR DP cells, to CD8αΒ SP TCRγδ+cells and to TCRαΒ+cells. Finally, we show that the γδ+subset of T-cell acute lymphoblastic leukemias (T-ALL) consists mainly of CD4 SP or DP phenotypes carrying significantly more activating Notch mutations than DN T-ALL. The latter suggests that activating Notch mutations in TCRγδ+thymocytes induce proliferation and differentiation along the DP pathway in vivo.

Multiple clonal Ig/TCR products: implications for interpretation of clonality findings (Article)

2011-12-09T00:00:00Z

Clonality assessment via analysis of immunoglobulin (Ig) and T cell receptor (TCR) gene rearrangements has become an important and valuable adjunct in the diagnostic process of suspect lymphoproliferations. One of the major issues in correct interpretation of clonality testing results appears to be the occurrence of multiple clonal PCR products. The presence of two different PCR products could reflect biclonality but can often more easily be attributed to the occurrence of biallelic rearrangements in a single clone. Furthermore, due to the specific configuration of the IGK and TCRB loci, multiple rearrangements can occur on one allele, resulting in the possibility that up to four PCR products could be compatible with a single clone. Finally, >2 clonal Ig/TCR products (>4 for IGK and TCRB) could reflect biclonality, oligoclonality, or even pseudoclonality. It is not always easy to distinguish between those options, but the use of duplicates will be helpful to determine reproducibility and relevance of the detected clonal PCR products. In conclusion, straightforward interpretation of clonality testing results can be hampered by the occurrence of multiple clonal products. Only careful consideration of immunobiological and technical explanations will prevent incorrect interpretation in such cases.

The EuroClonality website: information, education and support on clonality testing (Article)

2011-11-29T00:00:00Z

Clonality assessment is an established tool in the diagnosis of malignant lymphoma; however, the evaluation of immunoglobulin/T-cell receptor (Ig/TCR) gene rearrangement profiles is not always straightforward. Therefore, the EuroClonality group supports and advises diagnostic laboratories in their clonality assessments on samples from patients suspicious for lymphoma, who are seen in the routine diagnostic setting. The support for clonality assessment is provided via the EuroClonality website: http://www.euroclonality.org. The features and procedures of the website are presented in this paper.

Capillary electrophoresis single-strand conformation analysis (CE-SSCA) for clonality detection in lymphoproliferative disorders (Article)

2011-11-24T00:00:00Z

Clonality analysis is a critical tool for the diagnosis of suspect lymphoproliferative disorders. Amplification of the immunoglobulin and T cell receptor genes on genomic DNA from the suspect samples is followed by analysis of the PCR products to distinguish between polyclonal and clonal rearrangements. These analyses are based on electrophoresis in polyacrylamide gels after heteroduplex formation, or more frequently, GeneScan analysis is performed by capillary electrophoresis in automated DNA analysers, providing higher resolution and sensitivity. An alternative method for clonality analysis is the use of single-strand conformation analysis; however, this usually required labour intensive work with polyacrylamide gels and radioactive labelling. Within the EuroClonality group, we have developed a non-radioactive automated analysis based on capillary electrophoresis of single-strand PCR products that combines some of the benefits of heteroduplex and GeneScan analysis. This new method could be particularly suitable for challenging cases and could be implemented as an alternative to the more laborious heteroduplex analysis in standard gels in some instances.

Idiopathic retroperitoneal fibrosis mimicking malignant lymphoma (Article)

2011-10-06T00:00:00Z

We present a case of atypical idiopathic retroperitoneal fibrosis (iRPF) presenting as a large pelvic tumor, for which it proved difficult to exclude T-cell malignant lymphoma. Histopathological examination of biopsy material showed collagenous tissue and fat with an exuberant and predominant T-cell infiltrate, largely consisting of CD4+cells expressing the IL-2 receptor-α chain (CD25). Focal plasma cells were negative for the immunoglobulin G4 (IgG4) isotype. T-cell receptor gene rearrangement (TRGR) pattern showed a Gaussian distribution, in keeping with a polyclonal T-cell population. Awareness of the sometimes exuberant and predominant T-cell infiltrate in iRPF should lead to earlier consideration of this disorder. This is particularly the case where there is an atypically localized and/or extensive mass, for which early exclusion of monoclonality with TRGR may provide helpful. Immunohistochemical findings suggest that CD4+CD25+cells, which are part of a naturally occurring population of regulatory T-cells, may be involved in the pathogenesis of iRPF. © 2011 The Authors. Pathology International

Premature aging of circulating T cells in patients with end-stage renal disease (Article)

2011-07-02T00:00:00Z

Progressive loss of renal function is associated with a dysregulation of circulating T cells that may underlie their impaired T-cell immunity. Here we tested whether end-stage renal disease (ESRD)-related T-cell alterations are compatible with the concept of premature immunological aging. Younger patients (25-45 years old) with ESRD were found to resemble older healthy controls (60-80 years old) as they had a significant loss of naive T cells and a relative increase of memory T cells showing progressive terminal differentiation. A significant decrease in the content of T-cell receptor excision circles and telomere length in patients with ESRD confirmed these phenotypic data. The loss of naive T cells in patients with ESRD was associated with an excessive age-related decrease of recent thymic emigrants, indicating a premature decline in thymic function. Additionally, increased homeostatic proliferation of naive T cells was found in patients with ESRD, similar to that of older healthy individuals, with an increased susceptibility for activation-induced apoptosis. Therefore, both decreased thymic output and increased susceptibility of naive T cells for apoptosis may play a role in the loss of naive T cells in ESRD patients. Thus, our results are compatible with premature aging of the T-cell system of patients with ESRD comparable with that of healthy individuals 20-30 years older.

A restricted clonal T-cell receptor αβ repertoire in Sézary syndrome is indicative of superantigenic stimulation (Article)

2011-07-01T00:00:00Z

Background Sézary syndrome (SS) is a cutaneous T-cell lymphoma characterized by erythroderma, lymphadenopathy and malignant clonal T cells in the skin, lymph nodes and peripheral blood. A role for superantigens in the pathogenesis of SS has been postulated before. Objectives To investigate a putative involvement of chronic (super-)antigenic stimulation in driving T-cell expansion in SS. Methods Antigenic specificity of the T-cell receptor (TCR) was assayed by molecular analysis of the TCRA (n = 11) and TCRB (n = 28) genes, followed by detailed in silico analysis. Results Sequence analysis of clonally rearranged TCRB genes showed over-representation of Vβ8, Vβ13, Vβ17, Vβ21 and Vβ22, and under-representation of Vβ2 and Jβ1.1 when compared with healthy controls. No similarity was detected in amino acid motifs of the complementarity determining region 3 (CDR3). Analysis of TCRA rearrangements showed that there was no common Vα or Jα gene usage, and that TCRA CDR3 amino acid motifs were not highly similar. Conclusions The lack of clear stereotypic TCRA and TCRB CDR3 amino acid motifs would argue against involvement of a single common antigen in the pathogenesis of SS. Nevertheless, the skewing of Vβ and Jβ gene usage does seem to point to a restricted TCR repertoire, possibly as a result of superantigenic selection prior to neoplastic transformation. © 2011 The Authors. BJD

Posttranscriptional deregulation of MYC via PTEN constitutes a major alternative pathway of MYC activation in T-cell acute lymphoblastic leukemia (Article)

2011-06-16T00:00:00Z

Cumulative evidence indicates that MYC, one of the major downstream effectors of NOTCH1, is a critical component of T-cell acute lymphoblastic leukemia (T-ALL) oncogenesis and a potential candidate for targeted therapy. However, MYC is a complex oncogene, involving both fine protein dosage and cell-context dependency, and detailed understanding of MYC-mediated oncogenesis in T-ALL is still lacking. To better understand how MYC is interspersed in the complex T-ALL oncogenic networks, we performed a thorough molecular and biochemical analysis of MYC activation in a comprehensive collection of primary adult and pediatric patient samples. We find that MYC expression is highly variable, and that high MYC expression levels can be generated in a large number of cases in absence of NOTCH1/FBXW7 mutations, suggesting the occurrence of multiple activation pathways in addition to NOTCH1. Furthermore, we show that posttranscriptional deregulation of MYC constitutes a major alternative pathway of MYC activation in T-ALL, operating partly via the PI3K/AKT axis through down-regulation of PTEN, and that NOTCH1mmight play a dual transcriptional and posttranscriptional role in this process. Altogether, our data lend further support to the significance of therapeutic targeting of MYC and/or the PTEN/AKT pathways, both in GSI-resistant and identified NOTCH1-independent/MYC-mediated T-ALL patients.

Immunoglobulin sequence analysis and prognostication in CLL: Guidelines from the ERIC review board for reliable interpretation of problematic cases (Article)

2011-06-01T00:00:00Z

Immunoglobulin gene sequence analysis is widely utilized for prognostication in chronic lymphocytic leukemia (CLL) and the definition of standardized procedures has allowed reliable and reproducible results. Occasionally, a straightforward interpretation of the sequences is not possible because of the so-called problematic sequences that do not fit the classic interpretation and pose scientific questions at the cross-road between hematology and immunology. Thanks to a dedicated effort within the European Research Initiative on CLL (ERIC), we have now the possibility to present such cases, offer a scientific explanation and propose recommendations in terms of prognostication.

Integrated Transcript and Genome Analyses Reveal NKX2-1 and MEF2C as Potential Oncogenes in T Cell Acute Lymphoblastic Leukemia (Article)

2011-04-12T00:00:00Z

To identify oncogenic pathways in T cell acute lymphoblastic leukemia (T-ALL), we combined expression profiling of 117 pediatric patient samples and detailed molecular-cytogenetic analyses including the Chromosome Conformation Capture on Chip (4C) method. Two T-ALL subtypes were identified that lacked rearrangements of known oncogenes. One subtype associated with cortical arrest, expression of cell cycle genes, and ectopic NKX2-1 or NKX2-2 expression for which rearrangements were identified. The second subtype associated with immature T cell development and high expression of the MEF2C transcription factor as consequence of rearrangements of MEF2C, transcription factors that target MEF2C, or MEF2C-associated cofactors. We propose NKX2-1, NKX2-2, and MEF2C as T-ALL oncogenes that are activated by various rearrangements.

Natural killer cell receptor expression reflects the role of human cytomegalovirus in the pathogenesis of a subset of CD4+ T-cell large granular lymphocytosis (Article)

2011-03-01T00:00:00Z

A high frequency of CD4+T-cell large granular lymphocyte (T-LGL) lymphocytosis occurs in human leukocyte antigen (HLA) -DRB1*0701 individuals displaying monoclonal expansions of Vβ13.1+ CD4+T-cell clones, which specifically respond to human cytomegalovirus (HCMV) antigens. We previously reported the expression of natural killer (NK)-cell associated receptors (NKR) by HCMV-specific cytolytic CD4+T cells from healthy donors. In the present study a high expression of different NKR (i.e., NKG2D, killer Ig-like receptors (KIR), CD94, ILT2) was observed in CD4+T cells from both Vβ13.1- and Vβ13.1+ CD4+T-LGL cases. Remarkably, elevated numbers of CD94/NKG2C+ NK cells, previously shown to expand in association to HCMV infection, were preferentially found in Vβ13.1+ T-LGL, further supporting its role in the pathogenesis of a subset of CD4+T-LGL.

Skewed X chromosomal inactivation impacts T regulatory cell function in systemic sclerosis (Article)

2010-12-01T00:00:00Z

Objectives: To investigate the role of X chromosomal inactivation (XCI) in systemic sclerosis (SSc) and its effects on forkhead box P3 (Foxp3) expression in T regulatory cells (Tregs). Methods: 217 women with SSc and 107 healthy women (controls) were included in the study. From these subjects, DNA was isolated from total peripheral blood mononuclear cells, plasmacytoid dendritic cells, T cells, B cells, myeloid dendritic cells and monocytes after magnetic bead separation. All samples were assessed for skewed XCI patterns with the Human Androgen Receptor Assay. The outcome was assessed by linear regression. CD4+CD25+ cells were then isolated and intracellular Foxp3 expression was assessed by flow cytometry. Results: Skewing was not associated with increased age in patients with SSc, in contrast to the control population (r=0.45, p<0.0001). Taking this into account, a significantly higher frequency of skewed XCI was found in patients with SSc compared with controls (p=0.001). No difference in skewing was observed between the immune cell subsets. In addition, a higher concentration of Foxp3 + cells exhibiting a lower Foxp3 mean fluorescence intensity was found in the patients with SSc, with profound XCI skewing (both p<0.001) associated with less efficient suppressive activity (p=0.012). Conclusions: Skewed XCI plays a role in susceptibility to SSc, is not restricted and influences Foxp3 expression and the suppressive capacity of Tregs.

Estimating human age from T-cell DNA rearrangements (Article)

2010-11-23T00:00:00Z

Predicting human phenotypes from genotypes is a newly emerging field with relevance for personalized medicine [1] and forensics [2]. However, only a few phenotypic traits can currently be identified from DNA information with accuracies sufficient for practical applications [1], most notably human eye (iris) color [3]. It could be expected that individual age is too biologically complex to allow a simple and accurate molecular estimation from biological materials. Indeed, previously proposed genetic methods for human age estimation, based on the accumulation of mitochondrial DNA deletions or on telomere shortening, show low accuracies and various technical problems, and are therefore not suitable for practical applications [4]. Proposed biochemical methods, such as those based on the accumulation of D-aspartic acid, involve the destructive analysis of specific body parts (such as bones, teeth and ligaments), and suffer from technical issues and bio-degradation [4]. In the present study, we demonstrate that human individual age can be estimated accurately and reliably from blood using T-cell DNA rearrangements, and we provide a robust and sensitive real-time quantitative PCR protocol for application in various areas of bioscience.

Non-CLL-like monoclonal B-Cell lymphocytosis in the general population: Prevalence and phenotypic/genetic characteristics (Article)

2010-09-20T00:00:00Z

Background: Monoclonal B-cell lymphocytosis (MBL) indicates <5 × 109peripheral blood (PB) clonal B-cells/L in healthy individuals. In most cases, MBL cells show similar phenotypic/genetic features to chronic lymphocytic leukemia cells - CLL-like MBL - but little is known about non-CLL-like MBL. Methods: PB samples from 639 healthy individuals (46% men/54% women) >40 years old (62 ± 13years) with normal lymphocyte counts (2.1 ± 0.7 × 109/L) were immunophenotyped using high-sensitive flow cytometry, based on 8-color stainings and the screening for >5 × 106total PB leukocytes. Results: Thirteen subjects (2.0%; 9 males/4 females, aged 73 ± 10 years; absolute lymphocyte count: 2.4 ± 0.8 × 109/L) showed a non-CLL-like clonal B-cell population, whose frequency clearly increased with age: 0.4%, 3%, and 5.4% of subjects aged 40-59, 60-79, and ≥80 years, respectively. One single B-cell clone was detected in 9/13 cases, while two B-cell clones were found in 4/13 (n = 17 MBL populations). Nine MBL cell populations showed a CD5-phenotype (usually overlapping with marginal zone-derived (MZL) or lymphoplasmacytic (LPL) non-Hodgkin lymphoma (NHL) B-cells, or an unclassifiable NHL), but CD5-/+d(n = 3) and CD5+(n = 3 non-CLL-like MBL, consistent with a mantle-cell lymphoma (MCL)-like phenotype, and n = 2 CLL-like) MBL were also identified; iFISH supported the diagnosis in most cases. No preferential IGHV usage of B-cell receptor could be found. Twelve cases reevaluated at month +12 showed circulating clonal B-cells, at mean levels significantly higher than those initially detected. Conclusions: Non-CLL-like MBL cases frequently show biclonality, in association with MZL-, LPL-, MCL-like, or unclassifiable phenotypic profiles. As with CLL-like MBL, the frequency of non-CLL-like MBL increases with age, with a clear predominance of males.

Loss of juxtaposition of RAG-induced immunoglobulin DNA ends is implicated in the precursor B-cell differentiation defect in NBS patients. (Article)

2010-06-01T00:00:00Z

The Nijmegen breakage syndrome (NBS) is a rare inherited condition, characterized by microcephaly, radiation hypersensitivity, chromosomal instability, an increased incidence of (mostly) lymphoid malignancies, and immunodeficiency. NBS is caused by hypomorphic mutations in the NBN gene (8q21). The NBN protein is a subunit of the MRN (Mre11-Rad50-NBN) nuclear protein complex, which associates with double-strand breaks. The immunodeficiency in NBS patients can partly be explained by strongly reduced absolute numbers of B lymphocytes and T lymphocytes. We show that NBS patients have a disturbed precursor B-cell differentiation pattern and significant disturbances in the resolution of recombination activating gene-induced IGH breaks. However, the composition of the junctional regions as well as the gene segment usage of the reduced number of successful immunoglobulin gene rearrangements were highly similar to healthy controls. This indicates that the NBN defect leads to a quantitative defect in V(D)J recombination through loss of juxtaposition of recombination activating gene-induced DNA ends. The resulting reduction in bone marrow B-cell efflux appeared to be partly compensated by significantly increased proliferation of mature B cells. Based on these observations, we conclude that the quantitative defect will affect the B-cell receptor repertoire, thus contributing to the observed immunodeficiency in NBS patients.

Deletion of the protein tyrosine phosphatase gene PTPN2 in T-cell acute lymphoblastic leukemia (Article)

2010-06-01T00:00:00Z

PTPN2 (protein tyrosine phosphatase non-receptor type 2, also known as TC-PTP) is a cytosolic tyrosine phosphatase that functions as a negative regulator of a variety of tyrosine kinases and other signaling proteins1-3. In agreement with its role in the regulation of the immune system, PTPN2 was identified as a susceptibility locus for autoimmune diseases4,5. In this work, we describe the identification of focal deletions of PTPN2 in human T-cell acute lymphoblastic leukemia (T-ALL). Deletion of PTPN2 was specifically found in T-ALLs with aberrant expression of the TLX1 transcription factor oncogene, including four cases also expressing the NUP214-ABL1 tyrosine kinase. Knockdown of PTPN2 increased the proliferation and cytokine sensitivity of T-ALL cells. In addition, PTPN2 was identified as a negative regulator of NUP214-ABL1 kinase activity. Our study provides genetic and functional evidence for a tumor suppressor role of PTPN2 and suggests that expression of PTPN2 may modulate response to treatment.

PHF6 mutations in T-cell acute lymphoblastic leukemia (Article)

2010-04-01T00:00:00Z

Tumor suppressor genes on the X chromosome may skew the gender distribution of specific types of cancer. T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy with an increased incidence in males. In this study, we report the identification of inactivating mutations and deletions in the X-linked plant homeodomain finger 6 (PHF6) gene in 16% of pediatric and 38% of adult primary T-ALL samples. Notably, PHF6 mutations are almost exclusively found in T-ALL samples from male subjects. Mutational loss of PHF6 is importantly associated with leukemias driven by aberrant expression of the homeobox transcription factor oncogenes TLX1 and TLX3. Overall, these results identify PHF6 as a new X-linked tumor suppressor in T-ALL and point to a strong genetic interaction between PHF6 loss and aberrant expression of TLX transcription factors in the pathogenesis of this disease.

Generation of T cells from human embryonic stem cell-derived hematopoietic zones (Article)

2009-06-01T00:00:00Z

Human embryonic stem cells (hESC) are pluripotent stem cells. A major challenge in the field of hESC is the establishment of specific differentiation protocols that drives hESC down a particular lineage fate. So far, attempts to generate T cells from hESC in vitro were unsuccessful. In this study, we show that T cells can be generated in vitro from hESC-derived hematopoietic precursor cells present in hematopoietic zones (HZs). These zones are morphologically similar to blood islands during embryonic development, and are formed when hESC are cultured on OP9 stromal cells. Upon subsequent transfer of these HZs on OP9 cells expressing high levels of Delta-like 1 and in the presence of growth factors, cells expand and differentiate to T cells. Furthermore, we show that T cells derive exclusively from a CD34highCD43lowpopulation, further substantiating the notion that hESC-derived CD34highCD43lowcells are formed in HZs and are the only population containing multipotent hematopoietic precursor cells. Differentiation to T cells sequentially passes through the physiological intermediates: CD34+CD7+T/NK committed, CD7+CD4+CD8-immature single positive, CD4+CD8+double positive, and finally CD3+CD1-CD27+mature T cell stages. TCRαβ+and TCRγδ+T cells are generated. Mature T cells are polyclonal, proliferate, and secrete cytokines in response to mitogens. This protocol for the de novo generation of T cells from hESC could be clinically and scientifically relevant. Copyright

Genome-wide epigenetic analysis delineates a biologically distinct immature acute leukemia with myeloid/T-lymphoid features (Article)

2009-03-19T00:00:00Z

Acute myeloid leukemia is a heterogeneous disease from the molecular and biologic standpoints, and even patients with a specific gene expression profile may present clinical and molecular heterogeneity. We studied the epigenetic profiles of a cohort of patients who shared a common gene expression profile but differed in that only half of them harbored mutations of the CEBPA locus, whereas the rest presented with silencing of this gene and coexpression of certain T-cell markers. DNA methylation studies revealed that these 2 groups of patients could be readily segregated in an unsupervised fashion based on their DNA methylation profiles alone. Furthermore, CEBPA silencing was associated with the presence of an aberrant DNA hypermethylation signature, which was not present in the CEBPA mutant group. This aberrant hypermethylation occurred more frequently at sites within CpG islands. CEBPA-silenced leukemias also displayed marked hypermethylation compared with normal CD34+ hematopoietic cells, whereas CEBPA mutant cases showed only mild changes in DNA methylation compared with these normal progenitors. Biologically, CEBPA-silenced leukemias presented with a decreased response to myeloid growth factors in vitro.

17p13/TP53 deletion in B-CLL patients is associated with microRNA-34a downregulation (Letter To Editor)

2009-01-01T00:00:00Z

Expanded cells in monoclonal TCR-{alpha}{beta}+/CD4+/NKa+/CD8-/+dim T-LGL lymphocytosis recognize hCMV antigens (Article)

2008-12-01T00:00:00Z

Recent studies suggest the potential involvement of common antigenic stimuli on the ontogeny of monoclonal T-cell receptor (TCR)- αβ+/CD4+/NKa+/CD8-/+dimT-large granular lymphocyte (LGL) lymphocytosis. Because healthy persons show (oligo)clonal expansions of human cytomegalovirus (hCMV)-specific TCRVβ+/ CD4+/cytotoxic/memory T cells, we investigate the potential involvement of hCMV in the origin and/or expansion of monoclonal CD4+T-LGL. Peripheral blood samples from patients with monoclonal TCR-αβ+/ CD4+T-LGL lymphocytosis and other T-chronic lymphoproliferative disorders were evaluated for the specific functional response against hCMV and hEBV whole lysates as well as the "MQLIPDDYSNTHSTRYVTVK" hCMV peptide, which is specifically loaded in HLADRB1*0701 molecules. A detailed characterization of those genes that underwent changes in T-LGL cells responding to hCMV was performed by microarray gene expression profile analysis. Patients with TCR-αβ+/ CD4+T-LGL displayed a strong and characteristic hCMV-specific functional response, reproduced by the hCMV peptide in a subset of HLA-DRB1*0701+patients bearing TCRVβ13.1+clonal T cells. Gene expression profile showed that the hCMV-induced response affects genes involved in inflammatory and immune responses, cell cycle progression, resistance to apoptosis, and genetic instability. This is the first study providing evidence for the involvement of hCMV in the ontogeny of CD4+T-LGL, emerging as a model disorder to determine the potential implications of quite a focused CD4+/ cytotoxic immune response.

Unique morphological spectrum of lymphomas in Nijmegen breakage syndrome (NBS) patients with high frequency of consecutive lymphoma formation (Article)

2008-11-01T00:00:00Z

Nijmegen breakage syndrome (NBS) is an autosomal recessive disorder characterized by microcephaly, immunodeficiency, radiation hypersensitivity, chromosomal instability and increased incidence of malignancies. In Poland 105 NBS cases showing mutations in the NBS gene (nibrin, NBN), have been diagnosed, ∼53% of which have developed cancer, mainly (>90%) lymphoid malignancies. This study is based upon the largest reported group of NBS-associated lymphomas. The predominant lymphoma types found in these 14 NBS children were diffuse large B cell lymphoma (DLBCL) and T cell lymphoblastic lymphoma (T-LBL/ALL), all showing monoclonal Ig/TCR rearrangements. The spectrum of NBS lymphomas is completely different from sporadic paediatric lymphomas and lymphomas in other immunodeficient patients. Morphological and molecular analysis of consecutive lymphoproliferations in six NBS patients revealed two cases of true secondary lymphoma. Furthermore, 9/13 NBS patients with lymphomas analysed by split-signal FISH showed breaks in the Ig or TCR loci, several of which likely represent chromosome aberrations. The combined data would fit a model in which an NBN gene defect results in a higher frequency of DNA misrejoining during double-strand break (DSB) repair, thereby contributing to an increased likelihood of lymphoma formation in NBS patients.

Pitfalls in TCR gene clonality testing: teaching cases (Article)

2008-08-26T00:00:00Z

Clonality testing in T-lymphoproliferations has technically become relatively easy to perform in routine laboratories using standardized multiplex polymerase chain reaction protocols for T-cell receptor (TCR) gene analysis as developed by the BIOMED-2 Concerted Action BMH4-CT98-3936. Expertise with clonality diagnostics and knowledge about the biology of TCR gene recombination are essential for correct interpretation of TCR clonality data. Several immunobiological and technical pitfalls that should be taken into account to avoid misinterpretation of data are addressed in this report. Furthermore, we discuss the need to integrate the molecular data with those from immunohistology, and preferably also flow cytometric immunophenotyping, for appropriate interpretation. Such an interactive, multidisciplinary diagnostic model guarantees integration of available data to reach the most reliable diagnosis.

BMI1 as oncogenic candidate in a novel TCRB-associated chromosomal aberration in a patient with TCRγδ+ T-cell acute lymphoblastic leukemia (Article)

2008-06-01T00:00:00Z

T-cell receptor Vβ CDR3 oligoclonality frequently occurs in childhood refractory cytopenia (MDS-RC) and severe aplastic anemia (Article)

2008-06-01T00:00:00Z

(Very) severe acquired aplastic anemia ((v)SAA) and myelodysplastic syndrome (MDS) are rare diseases in childhood. (V)SAA is a bone marrow (BM) failure syndrome characterized by immune-mediated destruction of hematopoietic progenitors. MDS is a malignant clonal stem cell disorder, of which the hypoplastic variant is, in case of absence of a cytogenetic clone, difficult to separate from (v)SAA. Recently, studies provided a molecular signature of autoimmunity in adult (v)SAA, by showing oligoclonality based on the length of the TCR Vβ CDR3 region. We investigated retrospectively the frequency and the discriminative value of TCR Vβ CDR3 oligoclonality in pediatric (v)SAA and MDS patients. Peripheral blood (PB) and/or BM mononuclear cell samples of pediatric patients with (v)SAA (n=38), refractory cytopenia (MDS-RC) (n=28) and 18 controls were analysed via TCR Vβ heteroduplex PCR analysis of extracted RNA. A skewed TCR Vβ CDR3 repertoire was found in 21/38 (v)SAA and in 17/28 RC patients in contrast to 2/18 in the control group. These data suggest an overlapping group of RC and SAA patients that may share a common immune-mediated pathogenesis. Prospective studies are required to establish the clinical value of TCR Vβ CDR3 repertoire analysis to predict the clinical response in these patients.

Signaling pathways involved in the development of T-cell acute lymphoblastic leukemia (Article)

2008-04-01T00:00:00Z

Undersized, oversized? It is not one-size-fits-all in lymphoid clonality detection (Article)

2008-02-01T00:00:00Z

In clonality assessment in lymphoid malignancies expected size ranges of rearranged Ig/TCR PCR products are relevant and should be taken into account. Yet they should not be employed too strictly, as "undersized" and "oversized" products might still represent true rearrangement products. Now that Ig/TCR clonality testing has technically become relatively easy to perform in routine laboratories, correct interpretation becomes essential and preferably should be organized in close interaction between involved scientists.

Evaluation of functional single nucleotide polymorphisms of different genes coding for the immunoregulatory molecules in patients with monoclonal large granular lymphocyte lymphocytosis (Article)

2008-02-01T00:00:00Z

TCRαβ+/CD4+T-large granular lymphocyte (LGL) lymphocytosis is a subgroup of monoclonal T-LGL lymphoproliferative disorders that are different from the CD8+TCRαβT-LGL. An increasing evidence supports the involvement of a common antigen-driven mechanism in the etiology of TCRαβ+/CD4+T-LGL. In this study, we tested several polymorphic markers associated with chronic viral infections and autoimmune diseases, including cytotoxic T-lymphocyte antigen-4 (CTLA-4), tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10), interferon-γ (IFN-γ), RANTES, IL-1α, FAS, FAS-ligand (FASL), and NKG2D, to investigate the potential association of these immunogenetic factors with the development of T-LGL. Overall, 38 patients with CD4+T-LGL were analyzed and compared with a group of both CD8+/TCRαβ+T-LGL patients (n = 43) and a group of control subjects (n = 176). Our results did not show any clear association between the different single nucleotide polymorphisms (SNPs) analyzed and the development of CD4+/TCRαβ T-LGL. An increase in the frequency of -380 (AA/GA) TNF-α genotype associated with a greater production of this cytokine was found among CD8+T LGL patients in comparison to the CD4+LGL patients and the control group. Our results suggest that the frequency of SNP of the genes coding for the studied immunoregulatory molecules are not associated with the development of CD4+/TCRαβ+T-LGL.

Concomitant EBV-related B-cell proliferation and juvenile myelomonocytic leukemia in a 2-year-old child (Article)

2008-01-01T00:00:00Z

We present a case of a 2-year-old girl, who developed concomitant EBV-related B-cell proliferation and juvenile myelomonocytic leukemia (JMML). JMML was initially not recognized because of predominant B-cell proliferation. The activating N-RAS mutation was retrospectively already detectable at this early stage. Our findings support the hypothesis that EBV may contribute to JMML pathogenesis by stimulating pre-existing malignant clones. However, such stimulation of leukemic clone does not require the direct incorporation of the virus into myeloid progenitors. Most probably a cytokine burst resulting from EBV infection allows expansion of pre-existing malignant myeloid progenitors. Further studies are required to delineate exact mechanisms of EBV-related promotion of the JMML clone.

Prognostic significance of molecular-cytogenetic abnormalities in pediatric T-ALL is not explained by immunophenotypic differences (Article)

2008-01-01T00:00:00Z

Pediatric T-cell acute lymphoblastic leukemia (T-ALL) is characterized by chromosomal rearrangements possibly enforcing arrest at specific development stages. We studied the relationship between molecular-cytogenetic abnormalities and T-cell development stage to investigate whether arrest at specific stages can explain the prognostic significance of specific abnormalities. We extensively studied 72 pediatric T-ALL cases for genetic abnormalities and expression of transcription factors, NOTCH1 mutations and expression of specific CD markers. HOX11 cases were CD1 positive consistent with a cortical stage, but as 4/5 cases lacked cytoplasmatic-β expression, developmental arrest may precede β-selection. HOX11L2 was especially confined to immature and pre-AB developmental stages, but 3/17 HOX11L2 mature cases were restricted to the γδ-lineage. TAL1 rearrangements were restricted to the αβ-lineage with most cases being TCR-αβ positive. NOTCH1 mutations were present in all molecular-cytogenetic subgroups without restriction to a specific developmental stage. CALM-AF10 was associated with early relapse. TAL1 or HOX11L2 rearrangements were associated with trends to good and poor outcomes, respectively. Also cases with high vs low TAL1 expression levels demonstrated a trend toward good outcome. Most cases with lower TAL1 levels were HOX11L2 or CALM-AF10 positive. NOTCH1 mutations did not predict for outcome. Classification into T-cell developmental subgroups was not predictive for outcome.

Immunoglobulin/T-cell receptor clonality diagnostics (Article)

2007-12-01T00:00:00Z

Clonality testing in lymphoid malignancies has become technically relatively easy to perform in routine laboratories using standardized multiplex polymerase chain reaction protocols for Ig/T-cell receptor (TCR) gene analysis. Expertise with clonality diagnostics and knowledge about the biology of Ig/TCR recombination are essential for correct interpretation of the Ig/TCR clonality data. Several immunobiologic and technical pitfalls that should be taken into account to avoid misinterpretation of data are addressed in this review. Furthermore, the need to integrate the molecular data with that from (hemato-)pathology, and preferably also flowcytometric immunophenotyping for appropriate interpretation, is discussed. Such an interactive, multidisciplinary diagnostic model guarantees integration of all available data to reach the most reliable diagnosis.

Distinct gene expression profiles of acute myeloid/T-lymphoid leukemia with silenced CEBPA and mutations in NOTCH1 (Article)

2007-11-15T00:00:00Z

Gene expression profiling of acute myeloid leukemia (AML) allows the discovery of previously unrecognized molecular entities. Here, we identified a specific subgroup of AML, defined by an expression profile resembling that of AMLs with mutations in the myeloid transcription factor CCAAT/enhancer-binding protein alpha (C/EBPα), while lacking such mutations. We found that in these leukemias, the CEBPA gene was silenced, which was associated with frequent promoter hypermethylation. The leukemias phenotypically showed aberrant expression of T-cell genes, of which CD7 was most consistent. We identified 2 mechanisms that may contribute to this phenotype. First, absence of Cebpa led to up-regulation of specific T-cell transcripts (ie, Cd7 and Lck) in hematopoietic stem cells isolated from conditional Cebpa knockout mice. Second, the enhanced expression of TRIB2, which we identify here as a direct target of the T-cell commitment factor NOTCH1, suggested aberrantly activated Notch signaling. Putatively activating NOTCH1 mutations were found in several specimens of the newly identified subgroup, while a large set of control AMLs was mutation negative. A gene expression prediction signature allowed the detection of similar cases of leukemia in independent series of AML.

Immunoglobulin gene rearrangements and the pathogenesis of multiple myeloma (Article)

2007-11-01T00:00:00Z

The ability to rearrange the germ-line DNA to generate antibody diversity is an essential prerequisite for the production of a functional repertoire. While this is essential to prevent infections, it also represents the "Achilles heal" of the B-cell lineage, occasionally leading to malignant transformation of these cells by translocation of protooncogenes into the immunoglobulin (Ig) loci. However, in evolutionary terms this is a small price to pay for a functional immune system. The study of the configuration and rearrangements of the Ig gene loci has contributed extensively to our understanding of the natural history of development of myeloma. In addition to this, the analysis of Ig gene rearrangements in B-cell neoplasms provides information about the clonal origin of the disease, prognosis, as well as providing a clinical useful tool for clonality detection and minimal residual disease monitoring. Herein, we review the data currently available on both Ig gene rearrangements and protein patterns seen in myeloma with the aim of illustrating how this knowledge has contributed to our understanding of the pathobiology of myeloma.

The C-MYB locus is involved in chromosomal translocation and genomic duplications in human T-cell acute leukemia (T-ALL), the translocation defining a new T-ALL subtype in very young children (Article)

2007-08-15T00:00:00Z

The C-Myb transcription factor is essential for hematopoiesis, including in the T-cell lineage. The C-Myb locus is a common site of retroviral insertional mutagenesis, however no recurrent genomic involvement has been reported in human malignancies. Here, we identified 2 types of genomic alterations involving the C-MYB locus at 6q23 in human T-cell acute leukemia (T-ALL). First, we found a reciprocal translocation, t(6;7)(q23;q34), that juxtaposed the TCRB and C-MYB loci (n = 6 cases). Second, a genome-wide copy-number analysis by array-based comparative genomic hybridization (array-CGH) identified short somatic duplications that include C-MYB (MYBdup, n = 13 cases of 84 T-ALL, 15%). Expression analysis, including allele-specific approaches, showed stronger C-MYB expression in the MYB-rearranged cases compared with other T-ALLs, and a dramatically skewed C-MYB allele expression in the TCRB-MYB cases, which suggests that a translocation-driven deregulated expression may overcome a cellular attempt to down-regulate C-MYB. Strikingly, profiling of the T-ALLs by clinical, genomic, and large-scale gene expression analyses shows that the TCRB-MYB translocation defines a new T-ALL subtype associated with a very young age for T-cell leukemia (median, 2.2 years) and with a proliferation/mitosis expression signature. By contrast, the MYBdupalteration was associated with the previously defined T-ALL subtypes.

Different chromosomal breakpoints impact the level of LMO2 expression in T-ALL (Article)

2007-07-01T00:00:00Z

The t(11;14)(p13;q11) is presumed to arise from an erroneous T-cell receptor delta TCRD V(D)J recombination and to result in LMO2 activation. However, the mechanisms underlying this translocation and the resulting LMO2 activation are poorly defined. We performed combined in vivo, ex vivo, and in silico analyses on 9 new t(11;14)(p13;q11)-positive T-cell acute lymphoblastic leukemia (T-ALL) as well as normal thymocytes. Our data support the involvement of 2 distinct t(11;14)(p13;q11) V(D)J-related translocation mechanisms. We provide compelling evidence that removal of a negative regulatory element from the LMO2 locus, rather than juxtaposition to the TCRD enhancer, is the main determinant for LMO2 activation in the majority of t(11;14)(p13;q11) translocations. Furthermore, the position of the LMO2 breakpoints in T-ALL in the light of the occurrence of TCRD-LMO2 translocations in normal thymocytes points to a critical role for the exact breakpoint location in determining LMO2 activation levels and the consequent pressure for T-ALL development.

Novel insights into the development of T-cell acute lymphoblastic leukemia (Article)

2007-07-01T00:00:00Z

T-cell acute lymphoblastic leukemia (T-ALL) results from malignant transformation of immature cells of the T-cell lineage. T-ALL is a heterogeneous disease both clinically and genetically. It is generally accepted that T-ALL cells are the malignant counterpart of normally developing T cells in the thymus (thymocytes). Recent data using genome-wide gene expression profiling and assessment of the rearrangement status of the T-cell receptor loci confirm this notion. T-ALL cells differ from normal thymocytes in the overexpression of oncogenes that arise either from chromosomal translocations or via other mechanisms. In addition, signaling pathways that control the very first stages of thymocyte development (of note, the Notch and Wnt pathways) are involved in development of T-ALL in mice and humans when constitutively expressed. In particular, the activating mutations in the Notch pathways are believed to occur in a large proportion of human T-ALL. These findings on genetic events open up new therapeutic possibilities. Copyright

Monoclonal TCR-Vβ13.1+/CD4+/NKa +/CD8-/+dim T-LGL lymphocytosis: Evidence for an antigen-driven chronic T-cell stimulation origin (Article)

2007-06-01T00:00:00Z

Monoclonal TCRαβ+/CD4+T-large granular lymphocyte (T-LGL) lymphocytosis is a T-cell disorder with a restricted TCR-Vβ repertoire. In the present study we explored the potential association between the expanded TCR-Vβ families, the CDR3 sequences of the TCR-Vβ gene, and the HLA genotype of patients with monoclonal TCRαβ+/CD4+T-LGL lymphocytosis. For that purpose, 36 patients with monoclonal TCRαβ+/CD4+T-LGL lymphocytosis (15 TCR-Vβ13.1 versus 21 non-TCR-Vβ13.1) were selected. For each patient, both the HLA (class I and II) genotype and the DNA sequences of the VDJ-rearranged TCR-Vβ were analyzed. Our results show a clear association between the TCR-Vβ repertoire and the HLA genotype, all TCR-Vβ13.1+cases being HLADRB1* 0701 (P = .004). Interestingly, the HLA-DR7/TCR-Vβ13.1- restricted T-cell expansions displayed a highly homogeneous and strikingly similar TCR arising from the use of common TCR-Vβ gene segments, which shared (1) unique CDR3 structural features with a constantly short length, (2) similar combinatorial gene rearrangements with frequent usage of the Jβ1.1 gene, and (3) a homolog consensus protein sequence at recombination junctions. Overall, these findings strongly support the existence of a common antigendriven origin for monoclonal CD4+T-LGL lymphocytosis, with the identification of the exact peptides presented to the expanded T cells deserving further inves tigations.

Clinically and genetically atypical T-cell prolymphocytic leukemia underlines the relevance of a multidisciplinary diagnostic approach. (Article)

2007-03-01T00:00:00Z

Selective retention of herpes simplex virus-specific T cells in latently infected human trigeminal ganglia (Article)

2007-02-27T00:00:00Z

Primary infection with herpes simplex virus 1 (HSV-1) and varicella zoster virus (VZV) results in lifelong latent infections of neurons in sensory ganglia such as the trigeminal ganglia (TG). It has been postulated that T cells retained in TG inhibit reactivation of latent virus. The acquisition of TG specimens of individuals within hours after death offered the unique opportunity to characterize the phenotype and specificity of TG-resident T cells in humans. High numbers of activated CD8+T cells expressing a late effector memory phenotype were found to reside in latently infected TG. The T cell infiltrate was oligoclonal, and T cells selectively clustered around HSV-1 but not VZV latently infected neurons. Neuronal damage was not observed despite granzyme B expression by the neuron-interacting CD8+T cells. The TG-resident T cells, mainly CD8+T cells, were directed against HSV-1 and not to VZV, despite neuronal expression of VZV proteins. The results implicate that herpesvirus latency in human TG is associated with a local, persistent T cell response, comprising activated late effector memory CD8+T cells that appear to control HSV-1 latency by noncytolytic pathways. In contrast, T cells do not seem to be directly involved in controlling VZV latency in human TG.

Powerful strategy for polymerase chain reaction-based clonality assessment in T-cell malignancies Report of the BIOMED-2 Concerted Action BHM4 CT98-3936 (Article)

2007-02-01T00:00:00Z

Polymerase chain reaction (PCR) assessment of clonal T-cell receptor (TCR) and immunoglobulin (Ig) gene rearrangements is an important diagnostic tool in mature T-cell neoplasms. However, lack of standardized primers and PCR protocols has hampered comparability of data in previous clonality studies. To obtain reference values for Ig/ TCR rearrangement patterns, 19 European laboratories investigated 188 T-cell malignancies belonging to five World Health Organization-defined entities. The TCR/Ig spectrum of each sample was analyzed in duplicate in two different laboratories using the standardized BIOMED-2 PCR multiplex tubes accompanied by international pathology panel review. TCR clonality was detected in 99% (143/145) of all definite cases of T-cell prolymphocytic leukemia, T-cell large granular lymphocytic leukemia, peripheral T-cell lymphoma (unspecified) and angioimmunoblastic T-cell lymphoma (AILT), whereas nine of 43 anaplastic large cell lymphomas did not show clonal TCR rearrangements. Combined use of TCRB and TCRG genes revealed two or more clonal signals in 95% of all TCR clonal cases. Ig clonality was mostly restricted to AILT. Our study indicates that the BIOMED-2 multiplex PCR tubes provide a powerful strategy for clonality assessment in T-cell malignancies assisting the firm diagnosis of T-cell neoplasms. The detected TCR gene rearrangements can also be used as PCR targets for monitoring of minimal residual disease.

Polymerase chain reaction-based clonality testing in tissue samples with reactive lymphoproliferations: Usefulness and pitfalls. A report of the BIOMED-2 Concerted Action BMH4-CT98-3936 (Article)

2007-02-01T00:00:00Z

Lymphoproliferations are generally diagnosed via histomorphology and immunohistochemistry. Although mostly conclusive, occasionally the differential diagnosis between reactive lesions and malignant lymphomas is difficult. In such cases molecular clonality studies of immunoglobulin (Ig)/T-cell receptor (TCR) rearrangements can be useful. Here we address the issue of clonality assessment in 106 histologically defined reactive lesions, using the standardized BIOMED-2 Ig/TCR multiplex polymerase chain reaction (PCR) heteroduplex and GeneScan assays. Samples were reviewed nationally, except 10% random cases and cases with clonal results selected for additional international panel review. In total 75% (79/106) only showed polyclonal Ig/TCR targets (type I), whereas another 15% (16/106) represent probably polyclonal cases, with weak Ig/TCR (oligo)clonality in an otherwise polyclonal background (type II). Interestingly, in 10% (11/106) clear monoclonal Ig/ TCR products were observed (types III/IV), which prompted further pathological review. Clonal cases included two missed lymphomas in national review and nine cases that could be explained as diagnostically difficult cases or probable lymphomas upon additional review. Our data show that the BIOMED-2 Ig/TCR multiplex PCR assays are very helpful in confirming the polyclonal character in the vast majority of reactive lesions. However, clonality detection in a minority should lead to detailed pathological review, including close interaction between pathologist and molecular biologist.

Human T-cell lines with well-defined T-cell receptor gene rearrangements as controls for the BIOMED-2 multiplex polymerase chain reaction tubes (Article)

2007-02-01T00:00:00Z

The BIOMED-2 multiplex polymerase chain reaction (PCR) tubes for analysis of immunoglobulin and T-cell receptor (TCR) gene rearrangements have recently been introduced as a reliable and easy tool for clonality diagnostics in suspected lymphoproliferations. Quality and performance assessment of PCR-based clonality diagnostics is generally performed using human leukemia/lymphoma cell lines as controls. We evaluated the utility of 30 well-defined human T-cell lines for quality performance testing of the BIOMED-2 PCR primers and protocols. The PCR analyses of the TCR loci were backed up by Southern blot analysis. The clonal TCRB, TCRG and TCRD gene rearrangements were analyzed for gene segment usage and for the size and composition of their junctional regions. In 29 out of 30 cell lines, unique clonal TCR gene rearrangements could be easily detected. Besides their usefulness in molecular clonality diagnostics, these cell lines can now be authenticated based on their TCR gene rearrangement profile. This enables their correct use in molecular clonality diagnostics and in other cancer research studies.

Improved reliability of lymphoma diagnostics via PCR-based clonality testing: - Report of the BIOMED-2 Concerted Action BHM4-CT98-3936 (Article)

2007-02-01T00:00:00Z

The diagnosis of malignant lymphoma is a recognized difficult area in histopathology. Therefore, detection of clonality in a suspected lymphoproliferation is a valuable diagnostic criterion. We have developed primer sets for the detection of rearrangements in the B- and T-cell receptor genes as reliable tools for clonality assessment in lymphoproliferations suspected for lymphoma. In this issue of Leukemia, the participants of the BIOMED-2 Concerted Action CT98-3936 report on the validation of the newly developed clonality assays in various disease entities. Clonality was detected in 99% of all B-cell malignancies and in 94% of all T-cell malignancies, whereas the great majority of reactive lesions showed polyclonality. The combined BIOMED-2 results are summarized in a guideline, which can now be implemented in routine lymphoma diagnostics. The use of this standardized approach in patients with a suspect lymphoproliferation will result in improved diagnosis of malignant lymphoma.

BIOMED-2 multiplex immunoglobulin/T-cell receptor polymerase chain reaction protocols can reliably replace Southern blot analysis in routine clonality diagnostics (Article)

2005-01-01T00:00:00Z

To establish the most sensitive and efficient strategy of clonality diagnostics via immunoglobulin and T-cell receptor gene rearrangement studies in suspected lymphoproliferative disorders, we evaluated 300 samples (from 218 patients) submitted consecutively for routine diagnostics. All samples were studied using the BIOMED-2 multiplex polymerase chain reaction (PCR) protocol. In 176 samples, Southern blot (SB) data were also available, and the two types of molecular results were compared. Results of PCR and SB analysis of both T-cell receptor and immunoglobulin loci were concordant in 85% of samples. For discordant results, PCR results were more consistent with the final diagnosis in 73% of samples. No false-negative results were obtained by PCR analysis. In contrast, SB analysis failed to detect clonality in a relatively high number of samples, mainly in cases of low tumor burden. We conclude that the novel BIOMED-2 multiplex PCR strategy is of great value in diagnosing patients with suspected B- and T-cell proliferations. Because of its higher speed, efficiency, and sensitivity, it can reliably replace SB analysis in clonality diagnostics in a routine laboratory setting. Just as with SB results, PCR results should always be interpreted in the context of clinical, immunophenotypical, and histopathological data.

New insights on human T cell development by quantitative T cell receptor gene rearrangement studies and gene expression profiling (Article)

2005-01-01T00:00:00Z

To gain more insight into initiation and regulation of T cell receptor (TCR) gene rearrangement during human T cell development, we analyzed TCR gene rearrangements by quantitative PCR analysis in nine consecutive T cell developmental stages, including CD34+ lin- cord blood cells as a reference. The same stages were used for gene expression profiling using DNA microarrays. We show that TCR loci rearrange in a highly ordered way (TCRD-TCRG-TCRB-TCRA) and that the initiating Ddelta2-Ddelta3 rearrangement occurs at the most immature CD34+CD38-CD1a- stage. TCRB rearrangement starts at the CD34+CD38+CD1a- stage and complete in-frame TCRB rearrangements were first detected in the immature single positive stage. TCRB rearrangement data together with the PTCRA (pTalpha) expression pattern show that human TCRbeta-selection occurs at the CD34+CD38+CD1a+ stage. By combining the TCR rearrangement data with gene expression data, we identified candidate factors for the initiation/regulation of TCR recombination. Our data demonstrate that a number of key events occur earlier than assumed previously; therefore, human T cell development is much more similar to murine T cell development than reported before.

Unraveling the consecutive recombination events in the human IGK locus (Article)

2004-01-01T00:00:00Z

In addition to the classical Vkappa-Jkappa, Vkappa-kappa deleting element (Kde), and intron-Kde gene rearrangements, atypical recombinations involving Jkappa recombination signal sequence (RSS) or intronRSS elements can occur in the Igkappa (IGK) locus, as observed in human B cell malignancies. In-depth analysis revealed that atypical JkappaRSS-intronRSS, Vkappa-intronRSS, and JkappaRSS-Kde recombinations not only occur in B cell malignancies, but rather reflect physiological gene rearrangements present in normal human B cells as well. Excision circle analysis and recombination substrate assays can discriminate between single-step vs multistep rearrangements. Using this combined approach, we unraveled that the atypical Vkappa-intronRSS and JkappaRSS-Kde pseudohybrid joints most probably result from ongoing recombination following an initial aberrant JkappaRSS-intronRSS signal joint formation. Based on our observations in normal and malignant human B cells, a model is presented to describe the sequential (classical and atypical) recombination events in the human IGK locus and their estimated relative frequencies (0.2-1.0 vs < 0.03). The initial JkappaRSS-intronRSS signal joint formation (except for Jkappa1RSS-intronRSS) might be a side event of an active V(D)J recombination mechanism, but the subsequent formation of Vkappa-intronRSS and JkappaRSS-Kde pseudohybrid joints can represent an alternative pathway for IGK allele inactivation and allelic exclusion, in addition to classical Ckappa deletions. Although usage of this alternative pathway is limited, it seems essential for inactivation of those IGK alleles that have undergone initial aberrant recombinations, which might otherwise hamper selection of functional Ig L chain proteins.

Cortistatin rather than somatostatin as a potential endogenous ligand for somatostatin receptors in the human immune system (Article)

2003-01-01T00:00:00Z

Cells of the human immune system have been shown to express somatostatin receptors (sst). The expression of sst suggests a functional role of the peptide somatostatin (SS). However, SS expression has not been demonstrated yet in different human immune tissues. Therefore, we investigated by RT-PCR the expression of both SS and cortistatin (CST), a SS-like peptide, in various human lymphoid tissues and immune cells. We detected SS mRNA expression in the human thymus only, while not in thymocytes. CST mRNA was clearly expressed in the immune cells, lymphoid tissues, and bone marrow. Using quantitative RT-PCR, significant differences in expression levels between tissues were demonstrated. Expression of CST mRNA was up-regulated during differentiation of monocytes into macrophages and dendritic cells and could be up-regulated by lipopolysaccharide stimulation. Two differently sized cDNA fragments of CST were detected in the majority of cells and tissues. However, although both fragments were detected in nearly all T-cell lines (7 of 8), most of the B-cell lines expressed the short fragment only (8 of 10). Using autoradiography, we showed that CST displaced [125I-Tyr3]octreotide binding with relatively high affinity on human thymic tissue and sst2-expressing cells. This is the first extensive study demonstrating that human lymphoid tissues and immune cells express different levels of CST mRNA and that its expression can be regulated. On the basis of these observations, we hypothesize a role for CST as an endogenous ligand of at least the sst2 receptor in the human immune system, rather than SS itself.

The immunophenotypic and immunogenotypic B-cell differentiation arrest in bone marrow of RAG-deficient SCID patients corresponds to residual recombination activities of mutated RAG proteins (Article)

2002-01-01T00:00:00Z

The protein products of the recombination activating genes (RAG1 and RAG2) initiate the formation of immunoglobulin (Ig) and T-cell receptors, which are essential for B- and T-cell development, respectively. Mutations in the RAG genes result in severe combined immunodeficiency disease (SCID), generally characterized by the absence of mature B and T lymphocytes, but presence of natural killer (NK) cells. Biochemically, mutations in the RAG genes result either in nonfunctional proteins or in proteins with partial recombination activity. The mutated RAG genes of 9 patients from 7 families were analyzed for their recombination activity using extrachromosomal recombination substrates, rearrangement of endogenous Ig loci in RAG gene-transfected nonlymphoid cells, or the presence of Ig gene rearrangements in bone marrow (BM). Recombination activity was virtually absent in all 6 patients with mutations in the RAG core domains, but partial activity was present in the other 3 RAG-deficient patients, 2 of them having Omenn syndrome with oligoclonal T lymphocytes. Using 4-color flow cytometry, we could define the exact stage at which B-cell differentiation was arrested in the BM of 5 RAG-deficient SCID patients. In 4 of 5 patients, the absence of recombination activity was associated with a complete B-cell differentiation arrest at the transition from cytoplasmic (Cy) Igmu(-) pre-B-I cells to CyIgmu(+) pre-B-II cells. However, the fifth patient showed low frequencies of precursor B cells with CyIgmu and surface membrane IgM, in line with the partial recombination activity of the patient's mutated RAG gene and the detection of in-frame Ig gene rearrangements in BM.

Unraveling of the polymorphic C lambda 2-C lambda 3 amplification and the Ke+Oz- polymorphism in the human Ig lambda locus (Article)

2002-01-01T00:00:00Z

Two polymorphisms of the human Ig(lambda) (IGL) locus have been described. The first polymorphism concerns a single, 2- or 3-fold amplification of 5.4 kb of DNA in the C(lambda)2-C(lambda)3 region. The second polymorphism is the Mcg(-)Ke(+)Oz(-) isotype, which has only been defined via serological analyses in Bence-Jones proteins of multiple myeloma patients and was assumed to be encoded by a polymorphic C(lambda)2 segment because of its high homology with the Mcg(-)Ke(-)Oz(-) C(lambda)2 isotype. It has been speculated that the Mcg(-)Ke(+)Oz(-) isotype might be encoded by a C(lambda) gene segment of the amplified C(lambda)2-C(lambda)3 region. We now unraveled both IGL gene polymorphisms. The amplification polymorphism appeared to result from a duplication, triplication, or quadruplication of a functional J-C(lambda)2 region and is likely to have originated from unequal crossing over of the J-C(lambda)2 and J-C(lambda)3 region via a 2.2-kb homologous repeat. The amplification polymorphism was found to result in the presence of one to five extra functional J-C(lambda)2 per genome regions, leading to decreased Ig(kappa):Ig(lambda) ratios on normal peripheral blood B cells. Via sequence analysis, we demonstrated that the Mcg(-)Ke(+)Oz(-) isotype is encoded by a polymorphic C(lambda)2 segment that differs from the normal C(lambda)2 gene segment at a single nucleotide position. This polymorphism was identified in only 1.5% (2 of 134) of individuals without J-C(lambda)2 amplification polymorphism and was not found in the J-C(lambda)2 amplification polymorphism of 44 individuals, indicating that the two IGL gene polymorphisms are not linked.

Basic helix-loop-helix proteins E2A and HEB induce immature T-cell receptor rearrangements in nonlymphoid cells (Article)

2001-01-01T00:00:00Z

T-cell receptor (TCR) gene rearrangements are mediated via V(D)J recombination, which is strictly regulated during lymphoid differentiation, most probably through the action of specific transcription factors. Investigated was whether cotransfection of RAG1 and RAG2 genes in combination with lymphoid transcription factors can induce TCR gene rearrangements in nonlymphoid human cells. Transfection experiments showed that basic helix-loop-helix transcription factors E2A and HEB induce rearrangements in the TCRD locus (Ddelta2-Ddelta3 and Vdelta2-Ddelta3) and TCRG locus (psi Vgamma7-Jgamma2.3 and Vgamma8-Jgamma2.3). Analysis of these rearrangements and their circular excision products revealed some peculiar characteristics. The Vdelta2-Ddelta3 rearrangements were formed by direct coupling without intermediate Ddelta2 gene segment usage, and most Ddelta2-Ddelta3 recombinations occurred via direct coupling of the respective upstream and downstream recombination signal sequences (RSSs) with deletion of the Ddelta2 and Ddelta3 coding sequences. Subsequently, the E2A/HEB-induced TCR gene recombination patterns were compared with those in early thymocytes and acute lymphoblastic leukemias of T- and B-lineage origin, and it was found that the TCR rearrangements in the transfectants were early (immature) and not necessarily T-lineage specific. Apparently, some parts of the TCRD (Vdelta2-Ddelta region) and TCRG genes are accessible for recombination not only in T cells, but also in early B-cells and even in nonlymphoid cells if the appropriate transcription factors are present. The transfection system described here appeared to be useful for studying the accessibility of immunoglobulin and TCR genes for V(D)J recombination, but might also be applied to study the induction of RSS-mediated chromosome aberrations.

Ordered recombination of immunoglobulin light chain genes occurs at the IGK locus but seems less strict at the IGL locus (Article)

2001-01-01T00:00:00Z

Regulation of allelic and isotypic exclusion of human immunoglobulin (Ig) light-chain genes was studied in 113 chronic B-cell leukemias as a "single-cell" model that allowed complete analysis of each light chain allele. Our data show that monospecific Ig light chain expression is in about 90% of cases determined by ordered recombination: Igkappa gene (IGK) rearrangements, followed by IGK deletions and Iglambda gene (IGL) rearrangements, resulting in the presence of only one functional Ig light chain rearrangement. In about 10% (10 cases), 2 functional Ig light chain rearrangements (IGK/IGL or IGL/IGL, but not IGK/IGK) were identified. This might be explained by the fact that regulation of the ordered recombination process is not fully strict, particularly when the IGL locus is involved. Unfavorable somatic mutations followed by receptor editing might have contributed to this finding. Eight of these 10 cases indeed contained somatic mutations. In cases with 2 functional Ig light chain rearrangements, both alleles were transcribed, but monospecific Ig expression was still maintained. This suggests that in these cases allelelic exclusion is not regulated at the messenger RNA level but either at the level of translation or protein stability or via preferential pairing of Ig light and Ig heavy chains. Nevertheless, ordered rearrangement processes are the main determinant for monospecific Ig light chain expression.

Transcriptional control of t lymphocyte differentiation (Article)

2001-01-01T00:00:00Z

Initiation of gene transcription by transcription factors (TFs) is an important regulatory step in many developmental processes. The differentiation of T cell progenitors in the thymus is tightly controlled by signaling molecules, ultimately activating nuclear TFs that regulate the expression of T lineage-specific genes. During the last 2 years, significant progress has been made in our understanding of the signaling routes and TFs operating during the earliest stages of thymic differentiation at the CD4(-)CD8(-) double negative stage. Here we will review the TF families that play an important role in differentiation of thymocytes, particularly focusing on recent new information with respect to the Tcf, bHLH, GATA, and CBF/HES TF families.

Molecular and flow cytometric analysis of the Vbeta repertoire for clonality assessment in mature TCRalphabeta T-cell proliferations (Article)

2001-01-01T00:00:00Z

Clonality assessment through Southern blot (SB) analysis of TCRB genes or polymerase chain reaction (PCR) analysis of TCRG genes is important for diagnosing suspect mature T-cell proliferations. Clonality assessment through reverse transcription (RT)-PCR analysis of Vbeta-Cbeta transcripts and flow cytometry with a Vbeta antibody panel covering more than 65% of Vbeta domains was validated using 28 SB-defined clonal T-cell receptor (TCR)alphabeta(+) T-ALL samples and T-cell lines. Next, the diagnostic applicability of the V(beta) RT-PCR and flow cytometric clonality assays was studied in 47 mature T-cell proliferations. Clonal Vbeta-Cbeta RT-PCR products were detected in all 47 samples, whereas single Vbeta domain usage was found in 31 (66%) of 47 patients. The suspect leukemic cell populations in the other 16 patients showed a complete lack of Vbeta monoclonal antibody reactivity that was confirmed by molecular data showing the usage of Vbeta gene segments not covered by the applied Vbeta monoclonal antibodies. Nevertheless, this could be considered indirect evidence for the "clonal" character of these cells. Remarkably, RT-PCR revealed an oligoclonal pattern in addition to dominant Vbeta-Cbeta products and single Vbeta domain expression in many T-LGL proliferations, providing further evidence for the hypothesis raised earlier that T-LGL derive from polyclonal and oligoclonal proliferations of antigen-activated cytotoxic T cells. It is concluded that molecular Vbeta analysis serves to assess clonality in suspect T-cell proliferations. However, the faster and cheaper Vbeta antibody studies can be used as a powerful screening method for the detection of single Vbeta domain expression, followed by molecular studies in patients with more than 20% single Vbeta domain expression or large suspect T-cell populations (more than 50%-60%) without Vbeta reactivity.

The role of molecular analysis of immunoglobulin and T cell receptor gene rearrangements in the diagnosis of lymphoproliferative disorders (Article)

2001-01-01T00:00:00Z

AIMS: To investigate whether the analysis of immunoglobulin (Ig)/T cell receptor (TCR) rearrangements is useful in the diagnosis of lymphoproliferative disorders. METHODS: In a series of 107 consecutive cases with initial suspicion of non-Hodgkin's lymphoma (NHL), Southern blot (SB) analysis of Ig/TCR rearrangements was performed. RESULTS: In 98 of 100 histopathologically conclusive cases, Ig/TCR gene results were concordant. In one presumed diffuse large B cell lymphoma (DLCL) and one follicular lymphoma (FL) case no clonality could be detected by SB analysis, or by polymerase chain reaction (PCR) at second stage. In the DLCL, sampling error might have occurred; the FL was revised after an initial diagnosis of reactivity. In many of the histopathologically inconclusive cases Ig/TCR gene SB analysis was helpful, giving support for the histopathological suspicion. However, because of a lack of (clinical) follow up data this could not be confirmed in a few cases. CONCLUSIONS: Experienced haematopathologists or a pathologist panel can diagnose malignant versus reactive lesions in most cases without the need for Ig/TCR gene analysis and can select the 5-10% of cases that might benefit from molecular clonality studies.

Autoimmune lymphoproliferative syndrome (ALPS) in a child from consanguineous parents: a dominant or recessive disease? (Article)

2000-01-01T00:00:00Z

Autoimmune lymphoproliferative syndrome (ALPS) is characterized by autoimmune features and lymphoproliferations and is generally caused by defective Fas-mediated apoptosis. This report describes a child with clinical features of ALPS without detectable Fas expression on freshly isolated blood leukocytes. Detection of FAS transcripts via real-time quantitative PCR made a severe transcriptional defect unlikely. Sequencing of the FAS gene revealed a 20-nucleotide duplication in the last exon affecting the cytoplasmic signaling domain. The patient was homozygous for this mutation, whereas the consanguineous parents and the siblings were heterozygous. The patient reported here is a human homologue of the Fas-null mouse, inasmuch as she carries an autosomal homozygous mutation in the FAS gene and she shows the severe and accelerated ALPS phenotype. The heterozygous family members did not have the ALPS phenotype, indicating that the disease-causing FAS mutation in this family is autosomal recessive.

Molecular features responsible for the absence of immunoglobulin heavy chain protein synthesis in an IgH(-) subgroup of multiple myeloma (Article)

2000-01-01T00:00:00Z

This study involved 12 patients with multiple myeloma (MM), in whom malignant plasma cells did not contain immunoglobulin heavy chain (IgH) protein chains. Southern blot analysis revealed monoallelic J(H) gene rearrangements in 10 patients, biallelic rearrangement in 1 patient, and biallelic deletion of the J(H) and C(micro) regions in 1 patient. Heteroduplex polymerase chain reaction analysis enabled the identification and sequencing of 9 clonal J(H) gene rearrangements. Only 4 of the joinings were complete V(H)-(D)-J(H) rearrangements, including 3 in-frame rearrangements with evidence of somatic hypermutation. Five rearrangements concerned incomplete D(H)-J(H) joinings, mainly associated with deletion of the other allele. Curiously, in at least 1 of these 5 cases the second allele seemed to be in germline configuration, whereas the in-frame V(kappa)-J(kappa) gene rearrangements contained somatic mutations. The configuration of the IGH genes was further investigated by use of C(H) probes. In 5 patients the rearrangements in the J(H) and C(H) regions were not concordant, probably caused by illegitimate IGH class switch recombination (chromosomal translocations to 14q32. 3). These data indicate that in many IgH(-) MM patients illegitimate IGH class switch rearrangement or illegitimate deletion of the functional V(H)-(D(H))-J(H) allele are responsible for IgH negativity. For example, the exclusive presence of D(H)-J(H) rearrangements in combination with mutated IGK genes can only be explained in terms of normal B-cell development, if the second (functional) IGH allele is deleted, which was probably the case in most patients. Therefore, defects at the DNA level are responsible for the lack of IgH protein production in most IgH(-) MM patients.

Regulation of PDGF chain and receptor expression in human malignant mesothelioma cell lines (Doctoral Thesis)

1995-10-11T00:00:00Z

In normal, untransformed cells, growth is a tightly regulated process, A single cell is capable of controlling its growth by integrating the input from both positive growthstimulating and negative growth-inhibiting signals. Unrestrained cell proliferation is the hallmark of carcinogenesis and arises as a consequence of aberrations in this normal growth control. The importance of such disturbed growth-regulating mechanisms is underscored by the observation that in vitro tumour cells were found to proliferate independently of exogenous growth factors. The apparent ability to be able to grow without mitogenic factors supported the earlier suggestion of Temin that growth of transformed cells may be caused by endogenous production of growth factors. This concept was later extended to the autoerine growth stimulation model. It has become generally accepted that genetic damage is a central event in the process of loss of growth control. Disturbances in the growth-regulating mechanisms by changes in the genes til at govern these processes, consequently enable cells to escape normal growth control. Genes, whose products contribute to uncontrolled growth, once they are genetically altered, can be classified as oncogenes and tumour suppressor genes. In the former category such genetic alterations give rise to a gain-of-function resulting in positive growth stimulation (e.g. by changes in growth factor-encoding genes), whereas in the latter growth-inhibiting properties are lost.