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Molecular biology of hematological disorders.

At present, the mechanisms of normal hematopoiesis and the pathogenesis of various hematological disorders are being elucidated by molecular biological techniques, and information at the molecular level is being applied to the process of diagnosis and treatment in clinical practice. In 1961, Till & McCulloch first proved utilizing mouse spleen colony-forming technique to confirm that red cells, leukocytes and platelets are derived from common precursor cells (1). These cells are called pluripotent hematopoietic stem cells which have the ability to differentiate into all lineages of blood cells, and most importantly maintain self-renewal capacity. Therefore, stem cells are never depleted, and can supply each lineage of hematopoietic cells throughout life. Thereafter, the in vitro colony-forming technique was developed, and detailed analysis of hematopoiesis became possible using this technique (2). As a result, it was clarified that the differentiation, proliferation and apoptosis of hematopoietic cells are exquisitely controlled by various hematopoietic growth factors to maintain hematopoietic homeostasis. In the mid 1980s, molecular biological techniques developed so rapidly that molecular clonings of various hematopoietic growth factor genes were reported in succession. Thereafter, physiological functions and pharmacological effects were studied in detail using recombinant hematopoietic growth factors (3).