B-CELL CHRONIC LYMPHOCYTIC-LEUKEMIA POPULATIONS RESPOND STOCHASTICALLY TO COMBINATIONS OF GROWTH SIGNALS INVITRO

The ability of B-CLL lymphocyte populations to respond to cytokine sti mulation of mononuclear cultures was examined using 3-colour immunoflu orescence and multiparameter flow cytometry. The simultaneous detectio n of the membrane antigens CD5 and CD19, with the proliferation antige n Ki-67, allowed examination of the cell-cycle entry of the B-CLL lymp hocyte population. Upon stimulation with IFN-gamma, IFN-gamma + IL-2, TPA + IL-2 and TPA + IL-4, between 10 and 44% of B-CLL lymphocytes fro m 10 patients were stimulated to enter into cell-cycle. This B-CLL res ponse was notably more homogenous than the non-clonal lymphocyte respo nse. Except in the case of IFN-gamma alone, T-cell response did not co rrelate with B-CLL response, suggesting B-CLL lymphocytes respond dire ctly to combinations of growth signals. Considering the B-CLL populati on as homogenous, B-CLL lymphocytes respond in a stochastic manner.