[Control of leukaemic and normal myeloid haemopoietic cells (author's transl)]

The proliferation of myeloid haemopoietic stem cells is absolutely dependent on the presence of a heterogeneous group of proteins with colony stimulating activity (CSA). CSA is generated by monocytes and lymphocytes. The estimation of the molecular weight of colony stimulating factors from both cell lines demonstrates a non-identity. All monocyte derived molecular weight fractions induce differentiation of myeloid stem cells into granulocytes and macrophages. Lymphocyte derived factors have identical biologic activity, with the exeption of one factor which promotes differentiation into eosinophilic granulocytes. Granulocytes release factors which inhibit the growth of myeloid stem cells. Blasts from patients with acute leukaemia do not generate significant amounts of colony stimulating activity, however, in four of nine cases investigated the production of inhibitors for normal stem cell growth is found. Blasts from patients with chronic myeloid leukaemia in blast crisis may be capable of producing colony stimulating activity. Granulocytes from patients with chronic myeloid leukaemia in the chronic phase exhibit no measurable release of inhibitors of myeloid stem cells. In myeloid leukaemias the normal leukocyte population is entirely or partially replaced by leukaemic leukocytes; thus, the proliferation of leukaemic and normal haemopoietic cells is likely to occur under abnormal control.