Dijke, I.E.

Myelin ingestion alters macrophage antigen-presenting function in vitro and in vivo (Article)

2011-07-01T00:00:00Z

During MS, phagocytosing myelin-containing macrophages arise and lie in close proximity to T cells. To date, it has not been addressed whether these myelinladen macrophages have the capacity to present antigens to T cells and whether this contributes to inflammation in disease. We demonstrate that in vitro-generated human and mouse myelin-laden macrophages expressed MHC class I and II and costimulatory molecules and are thus well equipped for antigen presentation.uman myelin-laden macrophages exhibited normal endocytosis of particulate and soluble antigens. In addition, human myelin-laden macrophages elicited active T cell proliferation of nai{dotless}̈ve as well as memory T cells. Furthermore, mouse myelin-laden macrophages induced primary antigen-specific CD4+T cell proliferation in vivo but transiently diminished IFN-γ release. Functionally, MOG peptide-loaded myelin-laden mouse macrophages modestly but significantly reduced the severity of MOG peptide-induced EAE. These data show that myelin uptake results in the induction of a population of macrophages that retains antigen-presenting capacity and limits autoimmune-mediated disease.

Differential expression of the EGF-TM7 family members CD97 and EMR2 in lipid-laden macrophages in atherosclerosis, multiple sclerosis and Gaucher disease (Article)

2010-04-01T00:00:00Z

The members of the epidermal growth factor (EGF)-transmembrane (TM)7 family of adhesion class G-protein coupled receptors are abundantly expressed by cells of the myeloid lineage. A detailed investigation of their expression by functional subsets of activated macrophages is still lacking. Therefore, we determined the expression of CD97, EGF module-containing mucin-like receptor (EMR)2 and EMR3 by monocyte-derived macrophages experimentally polarized in vitro. This was compared to three types of disease-associated lipid-laden macrophages displaying an alternatively activated phenotype in situ. Polarization in vitro towards classically activated M1 versus alternatively activated M2 extremes of macrophage activation did not result in a congruent regulation of EGF-TM7 receptor mRNA and protein except for a down-regulation of CD97 by IL-10. In contrast, macrophages handling lipid overload in vivo displayed differences in the expression of CD97 and EMR2. While foamy macrophages in atherosclerotic vessels expressed both CD97 and EMR2, foam cells in multiple sclerosis brain expressed CD97, but only little EMR2. Foam cell formation in vitro by oxidized LDL and myelin did not affect CD97 or EMR2 expression. Gaucher spleen cells accumulating glucosylceramide expressed very high levels of CD97 and EMR2. These findings indicate that complex cellular expression programmes rather than activation modes regulate the expression of EGF-TM7 receptors in macrophages.

Regulatory T cells in alloreactivity after clinical heart transplantation (Article)

2009-10-01T00:00:00Z

Purpose of review As the knowledge of CD4+CD25bright+FoxP3+regulatory T cells in experimental transplant models grows, we need to understand how and to what extent these suppressor cells regulate donor-directed immune events in the transplantation clinic. This review focuses on the function of regulatory T cells in the peripheral blood and the transplanted organ of patients after heart transplantation during immunological quiescence and rejection. Recent findings Here, we present data that peripheral CD4+CD25bright+FoxP3+T cells of heart transplant patients who experience acute rejection have inadequate immune regulatory function in vitro compared with those of nonrejecting patients. During rejection, potent donor-specific T-cell suppressors are present in the transplanted organ. Summary The studies in transplant patients' show that the function of CD4+CD25bright+FoxP3+regulatory T cells in alloimmunity is to inhibit the activation of effector T cells, to prevent rejection, and to control the antidonor response at the graft itself at later stages of immune reactivity.

High levels of myeloid-related protein 14 in human atherosclerotic plaques correlate with the characteristics of rupture-prone lesions (Article)

2009-08-01T00:00:00Z

OBJECTIVE-: Atherosclerotic plaque rupture can lead to severe complications such as myocardial infarction and stroke. Myeloid related protein (Mrp)-14, Mrp-8, and Mrp-8/14 complex are inflammatory markers associated with myocardial infarction. It is, however, unknown whether Mrps are associated with a rupture-prone plaque phenotype. In this study, we determined the association between Mrp-14, -8, -8/14 plaque levels and plaque characteristics. METHODS AND RESULTS-: In 186 human carotid plaques, levels of Mrp-14, -8, and -8/14 were quantified using ELISA. High levels of Mrp-14 were found in lesions with a large lipid core, high macrophage staining, and low smooth muscle cell and collagen amount. Plaques with high levels of Mrp-14 contained high interleukin (IL)-6, IL-8, matrix metalloprotease (MMP)-8, MMP-9, and low MMP-2 concentrations. Mrp-8 and Mrp-8/14 showed a similar trend. Within plaques, a subset of nonfoam macrophages expressed Mrp-8 and Mrp-14 and the percentage of Mrp-positive macrophages was higher in rupture-prone lesions compared to stable ones. In vitro, this subset of macrophages does not acquire a foamy phenotype when fed oxLDL. CONCLUSION-: Mrp-14 is strongly associated with the histopathologic features and the inflammatory status of rupture-prone atherosclerotic lesions, identifying Mrp-14 as a local marker for these plaques.

Inadequate immune regulatory function of CD4+CD25bright+FoxP3+ T cells in heart transplant patients who experience acute cellular rejection (Article)

2009-04-27T00:00:00Z

BACKGROUND.: CD4CD25FoxP3 regulatory T cells are suppressors of antigen-activated immune reactivity. Here, we assessed the clinically relevant role of these cells in the control of immune responses directed to a transplanted heart. METHODS.: We investigated the phenotype and function of peripheral CD4CD25FoxP3 T cells in heart transplant patients free from acute rejections (n=9) and in rejectors (n=12) before and during acute cellular rejection. RESULTS.: Between rejectors and nonrejectors, the proportion of CD4CD25 T cells and of FoxP3 cells within this population was comparable. Yet, CD4CD25FoxP3 T cells of rejectors had a higher CD127 expression than those of nonrejectors (P=0.0001). Depletion of CD4CD25 T cells from peripheral blood mononuclear cells increased the antidonor proliferative response of both nonrejectors (P≤0.0005) and rejectors (P≤0.03). In rejectors, however, only a 2-fold increase was measured, whereas the nonrejectors' response became 14 times higher (P=0.002). Reconstitution of CD4CD25 T cells only suppressed the overall antidonor proliferative response of CD25 responder cells of nonrejectors significantly (P=0.001). Moreover, the percentage inhibition of the response was higher in nonrejectors than in rejectors (P=0.02). Analyses of pretransplant samples revealed that CD4CD25 T cells of rejectors already had a lower suppressive capacity than those of nonrejectors before transplantation (P=0.04). CONCLUSION.: CD4CD25FoxP3 T cells of heart transplant patients who experience acute rejection had an up-regulated CD127 expression and an inadequate regulatory function compared with those of nonrejecting patients. Our observations suggest that the function of circulating CD4CD25FoxP3 regulatory T cells may be pivotal for the prevention of acute cellular rejection after clinical heart transplantation.

Donor-specific immune regulation by CD8+ lymphocytes expanded from rejecting human cardiac allografts (Article)

2009-02-01T00:00:00Z

To assess whether regulatory T cells are present in rejecting human cardiac allografts, we performed functional analyses of graft lymphocytes (GLs) expanded from endomyocardial biopsies (EMB; n = 5) with histological signs of acute cellular rejection. The GL cultures were tested for their proliferative capacity and regulatory activity on allogeneic-stimulated peripheral blood mononuclear cells (PBMC) of the patient (ratio PBMC:GLs = 5:1). Three of these GL cultures were hyporesponsive to donor antigens and suppressed the antidonor proliferative T-cell response of PBMC, but not the anti-third-party response. Interestingly, it was the CD8+GL subset of these cultures that inhibited the antidonor response (65-91% inhibition of the proportion of proliferating cells); the CD4+GLs of the expanded GL cultures were not suppressive. In conclusion, CD8+GLs expanded from rejecting human cardiac allografts can exhibit donor-specific immune regulatory activities in vitro. We suggest that during acute cellular rejection, GLs may not only consist of graft-destructing effector T cells, but also of cells of the CD8+type with the potential to specifically inhibit antidonor immune reactivity.

Immune Regulation after Heart Transplantation: Dynamics of regulatory T cells in the transplanted heart and peripheral blood (Doctoral Thesis)

2009-01-14T00:00:00Z

Heart transplantation has become a rapidly evolving therapy for end-stage heart failure. To reduce the risk of rejection of the transplanted organ, patients are treated with immunosuppressive therapy. However, as immunosuppressive drugs carry severe side effects, true transplant tolerance (i.e., long-lasting nonreactivity of the immune system to donor antigens in the absence of immunosuppressive drugs) is a major goal in transplantation research. T-cell-mediated regulation of donor-reactive cells is one of the mechanisms that may be involved in the induction and maintenance of graft acceptance after organ transplantation. The identification and characterization of regulatory T cells that can control the anti-donor immune reactivity has therefore become the focus of many studies. Research in experimental transplant models has demonstrated that these regulators are important for the prevention of allograft rejection and the induction of transplant tolerance.1! -4 Yet, it remains to be elucidated whether regulatory T cells control anti-donor immune reactivity in immunosuppressed organ transplant patients, thereby inducing and maintaining donor-specific nonresponsiveness. The central aim of this thesis was to investigate the role of regulatory T cells in the control of immune responses directed to the transplanted graft of heart transplant patients. We focused on two compartments where functional regulatory T cells may be present, i.e. the transplanted heart and the peripheral blood. Our studies demonstrated that various regulatory T-cell populations present in these compartments play a role in immunological processes, such as immunological quiescence and acute cellular rejection.

Regulatory T cells after organ transplantation: Where does their action take place? (Article)

2008-07-01T00:00:00Z

Regulatory T cells are considered to be pivotal for the induction of tolerance to donor antigens. In the past decades, several regulatory T-cell subsets have been identified, such as CD4+CD25+ regulatory T cells and the CD8+CD28- suppressor T cells. Although many studies have investigated the role of these regulators in transplant tolerance, relatively little attention has focused on the exact place where these cells suppress immune responses directed to donor antigens. The localization of regulatory T cells may influence their effect on allogeneic immune responses. More insight into the localization and migration of regulatory T cells in transplant recipients is therefore important, especially when these cells are to be used for monitoring purposes and for cellular immune therapy. In the present review we summarize current knowledge about the presence of functional donor-directed regulatory T cells in the secondary lymphoid organs, peripheral blood, and the transplanted organ itself. In addition, we discuss the importance of the appropriate localization for the control of anti-donor immune reactivity.

The Control of Anti-Donor Immune Responses by Regulatory T Cells in Organ Transplant Patients (Article)

2008-06-01T00:00:00Z

The role of regulatory T cells in the induction and maintenance of transplant tolerance has been widely investigated in experimental animal models. Their involvement in the regulation of allogeneic immune reactivity in immunosuppressed organ transplant patients, however, remains unclear. Measurements of regulatory T cells after clinical organ transplantation may contribute to understanding their role in anti-donor immune responses. Several studies have investigated the frequency and/or immune regulatory function of peripheral regulatory T-cell populations, such as, the CD4+CD25+regulatory T cells or the CD8+CD28-suppressor T cells, in clinically stable organ transplant patients and patients with acute or chronic rejection. This review summarizes these studies and discusses the correlations found between the number and function of regulatory T cells and the immunological state of the patient. This knowledge is warranted for a better understanding of the control of allogeneic immune responses by regulatory T cells. Subsequently, monitoring regulatory T cells may help us to identify patients in whom the anti-donor reactivity is actively suppressed.

FOXP3 mRNA expression analysis in the peripheral blood and allograft of heart transplant patients (Article)

2008-01-01T00:00:00Z

Previously, we demonstrated in heart transplant patients that FOXP3, a gene required for the development and function of regulatory T cells, was highly expressed in the graft during an acute cellular rejection. In this study, we analyzed whether the FOXP3 gene expression in the peripheral blood also reflects anti-donor immune responses, and therefore may provide clues for non-invasive detection of non-responsiveness or acute rejection. We examined the FOXP3 expression patterns of peripheral blood mononuclear cells (PBMC; n = 69) of 19 heart transplant patients during quiescence and rejection in comparison with those of endomyocardial biopsies (EMB; n = 75) of 24 heart transplant patients. While the FOXP3 mRNA levels were abundantly expressed in rejecting EMB (ISHLT rejection grade > 1R) compared with EMB without histological evidence of myocardial damage (ISHLT rejection grade 0R-1R; p = 0.003), no association with rejection or non-responsiveness was found for the FOXP3 mRNA levels in the peripheral blood. Thus, in contrast to intragraft FOXP3 gene expression, the peripheral FOXP3 mRNA levels lack correlation with anti-donor immune responses in the graft, and, consequently, FOXP3 does not appear to be a potential candidate gene for non-invasive diagnosis of non-responsiveness or rejection.

Interleukin-21: An interleukin-2 dependent player in rejection processes (Article)

2007-06-01T00:00:00Z

BACKGROUND. Interleukin (IL)-21 is the most recently described cytokine that signals via the common cytokine receptor (γc), is produced by activated CD4+ T-cells, and regulates expansion and effector function of CD8+ T-cells. MATERIALS. To explore the actions of IL-21 with other γc-dependent cytokines in alloreactivity, mRNA expression of IL-21, IL-21R α-chain, and IL-2 proliferation and cytotoxicity was measured after stimulation in mixed lymphocyte reactions. Additionally, IL-21 and IL-21R α-chain expression was studied in biopsies of heart transplant patients. RESULTS. Analysis of mRNA expression levels of allostimulated T-cells showed a 10-fold induction of IL-21 and IL-21R α-chain. Interestingly, induction of IL-21 was highly dependent on IL-2 (as in the presence of anti-IL-2, anti-IL-2R α-chain, and the immunosuppressive drugs cyclosporine A, tacrolimus, and rapamycin) the transcription of IL-21 was almost completely inhibited, whereas in the presence of exogenous IL-2 the mRNA expression of IL-21 was even more upregulated. IL-21 functioned as a costimulator for IL-2 to augment proliferation and cytotoxic responses, while blockade of the IL-2 route abrogated these functions of IL-21. Blockade of the IL-21 route by anti-IL-21R α-chain monoclonal antibodies inhibited the proliferation of alloactivated T-cells. Also, in vivo alloreactivity was associated with IL-21/IL-21R α-chain expression. After heart transplantation, the highest intragraft IL-21, IL-21R α-chain, and IL-2 mRNA expression levels were measured during acute rejection (P<0.001, P=0.01, P=0.03). CONCLUSION. IL-21 is a critical cytokine for IL-2 dependent immune processes. Blockade of the IL-21 pathway may provide a new perspective for the treatment of allogeneic responses in patients after transplantation.

Intragraft FOXP3 mRNA expression reflects antidonor immune reactivity in cardiac allograft patients (Article)

2007-06-01T00:00:00Z

BACKGROUND. Regulatory FOXP3+ T cells control immune responses of effector T cells. However, whether these cells regulate antidonor responses in the graft of cardiac allograft patients is unknown. Therefore, we analyzed the gene expression profiles of regulatory and effector T-cell markers during immunological quiescence and acute rejection. METHODS. Quantitative real-time polymerase chain reaction was used to analyze mRNA expression levels in time-zero specimens (n=24) and endomyocardial biopsies (EMB; n=72) of cardiac allograft patients who remained free from rejection (nonrejectors; n=12) and patients with at least one histologically proven acute rejection episode (rejectors; International Society for Heart and Lung Transplantation [ISHLT] rejection grade >2; n=12). RESULTS. For all analyzed regulatory and effector T-cell markers, mRNA expression levels were increased in biopsies taken after heart transplantation compared with those in time-zero specimens. Posttransplantation, the FOXP3 mRNA levels were higher in EMB assigned to a higher ISHLT rejection grade than the biopsies with grade 0: the highest mRNA levels were detected in the rejection biopsies (rejection grade >2; P=0.003). In addition, the mRNA levels of CD25, glucocorticoid-induced TNF receptor family-related gene, cytotoxic T lymphocyte-associated antigen 4, interleukin-2, and granzyme B were also significantly higher in rejecting EMB than in nonrejecting EMB (rejection grade ≤2). This increase in expression levels in relation to the histological rejection grade was only observed in patients who developed an acute rejection episode; the mRNA levels of nonrejectors remained stable irrespective of ISHLT rejection grade. CONCLUSIONS. These observations suggest that, after clinical heart transplantation, FOXP3+ T cells do not prevent acute rejection, but rather are a response to antidonor effector T-cell activity.