Transplantation of Cultured Hemopoietic Stem Cells

The hemopoietic system contains a variety of cells with differing capacities for self-renewal, differentiation and maturation, resulting ultimately in the production of the mature blood elements. The earliest, functionally recognisable cell is the spleen colony forming cell or CFU-S, described by Till and McCulloch (1961), which possesses extensive self-renewal ability and pluripotentiality (Metcalf and Moore, 1971, Review). From the CFU-S are derived the various precursor cells ie. committed in pathway of differentiation but retaining extensive proliferative ability, and in vitro systems exist for the clonal proliferation of most of these populations. Granulocyte precursor cells (CFU-C) are recognised by their ability to form colonies containing granulocytes and macrophages, in soft gel media, in the presence of appropriate colony-stimulating factors (CSF) (Bradley and Metcalf, 1966; Pluznik and Sachs, 1966), erythroid precursor cells can be functionally separated into two or more compartments, reflecting their in vitro proliferative ability and their response to erythropoietin and other factors (Stephenson et al., 1971; McLeod et al., 1974; Heath et al., 1976;Iscove, 1978), and include the BFU-E and CFU-E. Furthermore, megakaryocyte progenitor cells can also be induced to undergo clonal proliferation in vitro (Metcalf et al., 1975a) and in the presence of suitable mitogens and growth promoting factors B and T lymphocyte colony formation can also be induced (Metcalf et al., 1975b; Sredni et al., 1976).