Stimulatory activity of PHA-LCM for normal human hemopoietic progenitors and leukemic blast cell precursors: separation by isoelectric focusing.

Medium conditioned by leukocytes in the presence of phytohemagglutinin (PHA-LCM) promotes growth of human hemopoietic progenitors (CFU-GEMM, BFU-E, CFU-C) and precursors of leukemic blast cells. PHA-LCM was separated by isoelectric focusing and each fraction tested with nonadherent cells of normal individuals as well as blast cells from two patients with acute myelogenous leukemia. Activity profiles for CFU-GEMM, BFU-E and CFU-C ranged form pH 5.0-6.5. The profile for activity stimulatory for leukemic blast cells was broader and ranged from pH 5.5-7.5. Although some overlap was observed, the main peaks of stimulatory activity for normally differentiating progenitors and precursors of leukemic blast cells were separable with respect to their isoelectric point.