Stimulation of human haemopoietic cells by colony stimulating factors: sensitivity of leukaemia cells.

The sensitivity of populations of human granulocyte precursors to factors with colony stimulating activity (CSA) was assessed in agar culture in vitro. The mean threshold of stimulation was estimated by analysis of dose-response curves of clone growth against concentration of CSA. This method of assessment has the advantage that CSA production by cells contaminating the population under test does not affect results. Marrow cells from patients with acute myeloid leukaemia were less sensitive to CSA than marrow cells from normal individuals. Sensitivities of cells from chronic granulocytic leukaemia and from chronic myelomonocytic leukaemia were within the normal range, but this group also tended to require more CSA than controls. In addition, sensitivities of granulocyte precursors from patients with acute myeloid leukemia were closely related to the culture pattern, and thus to the remission probability. The significance of this relationship is discussed.