Regulation of human peripheral blood BFU-E growth in vitro by leukaemic B-lymphocytes.

We report a stimulating effect of leukaemic B-lymphocytes from anaemic and non-anaemic patients with CLL on the proliferation of normal peripheral blood BFU-E. Coculture of leukaemic B-cells at various concentrations (2.5 X 10(3)-10(6)) with 2.5 X 10(5) mononuclear cells from normal peripheral blood increased the number of BFU-E derived erythroid colonies. The same effect was observed when the number of target cells was varied in the presence of a fixed number of B-lymphocytes, with a clear linear relationship. B-cell conditioned medium gave a similar increase when added to the culture instead of B-cells. At high concentration of B-cells from anaemic patients, the size of the colonies was increased and a large number of macroscopic colonies was seen. The place of the B-cells in the regulation of erythroid progenitors in relation to monocytes and T-lymphocytes has still to be established.