Blood consists of serum and three other main ingredients: erythrocytes (red blood cells), thrombocytes (platelets) and leukocytes (white blood cells). Leukocytes normally compose less than 1% of the blood volume but have important functions in our defense against foreign and endogenous pathogens. Many different leukocytes can be distinguished, the main types being lymphocytes (~75% T-cells, ~25% B-cells), monocytes and granulocytes. All these different blood cells arise through distinct and tightly controlled developmental stages from hematopoietic precursor cells, which reside in the bone marrow and thymus (Figure 1). However, sequential mutations, chromosomal rearrangements and epigenetic changes can cause a precursor cell to be blocked from further differentiation and to start proliferate in a uncontrollable manner which results in cancer. Uncontrolled proliferation of blood precursor cells is called leukemia. Different types of leukemia are distinguished based on their lineage of origin; myeloid or lymphoblastic leukemia. Lymphoblastic leukemia can be further divided into Bcell precursor (BCP) or T-cell lymphoblastic leukemia. In acute lymphoblastic leukemia malignant cells are arrested at a relative immature stage whereas in chronic lymphocytic leukemia, cells have a more differentiated phenotype.

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R. Pieters (Rob)
Erasmus University Rotterdam
Dutch Cancer Society (KWF), Pediatric Oncology Foundation Rotterdam (KOCR)
Erasmus MC: University Medical Center Rotterdam

Homminga, I. (2011, November 30). Gene-expression profiles and oncogenes in pediatric T-cell acute lymphoblastic leukemia. Erasmus University Rotterdam. Retrieved from