Pluripotent stem cell pool

The pluripotent stem cell pool in bone marrow gives rise to both lymphocytes and the myeloid precursors that differentiate into erythrocytes, thrombocytes, and several different granulocytes (Figure 16-1). 

All mature blood cells arise from primitive hematopoietic cells in the bone marrow, the pluripotent stem cells. Approximately 0.1% of the nucleated cells of the bone marrow are pluripotent stem cells and approximately 5% of these cells may be actively cycling at any one time. The stem cell pool maintains itself through a process of asymmetrical cell division when a stem cell divides, one daughter cell remains a stem cell and the other becomes a committed colony-forming cell (CFC). The proliferation and differentiation of CFCs are controlled by hematopoietic growth factors. The hematopoietic growth factors stimulate cell division, differentiation and maturation, and convert the dividing cells into a population of terminally differentiated functional cells. 

A basic understanding of normal hematopoiesis is needed before one can understand the pathogenesis of leukemia. The reader is referred to Chap. 98 for a detailed discussion of hematopoiesis. Normal hematopoiesis consists of multiple well-orchestrated steps of cellular development. A pool of pluripotent stem cells undergoes differentiation, proliferation, and maturation, to form the mature blood cells seen in the peripheral circulation. These pluripotent stem cells initially differentiate to form two distinct stem cell pools. The myeloid stem cell gives rise to six types of blood cells (erythrocytes, platelets, monocytes, basophils, neutrophils, and eosinophils), while the lymphoid stem cell differentiates to form circulating B and T lymphocytes. Leukemia may develop at any stage and within any cell line. 

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