Clonal growth of human megakaryocyte progenitors in serum-free cultures: effect of recombinant human interleukin 3.

Human megakaryocyte colony formation was observed in serum-free agar cultures with a medium containing deionized bovine serum albumin, iron-saturated transferrin, 2-mercaptoethanol, and recombinant human interleukin 3 (IL-3). Megakaryocyte colonies were identified in situ by the alkaline phosphatase anti-alkaline phosphatase technique, using monoclonal antibody against platelet glycoprotein IIb/IIIa. Colony numbers reached a peak at day 14, with a mean of 47 megakaryocyte colonies (range 23-104) per 2 x 10(5) bone marrow mononuclear cells. Recombinant human IL-3 stimulated the growth of megakaryocyte progenitors. Similar results were obtained using nonadherent, T-cell-depleted mononuclear cells. These findings suggest that IL-3 stimulates the growth of megakaryocyte progenitors directly without activation of accessory cells, or the requirement of factors present in the serum or plasma. This serum-free culture system may be useful for studying the effects of purified natural and recombinant biological regulators on human megakaryocyte progenitors.