CFU - M - Derived Human Megakaryocytes Synthesize Glycoproteins lib and lila

Human megakaryocytes have been shown by immunofluorescent techniques to express platelet glycoprotein lIb/Illa antigen. We report evidence that megakaryocytes derived from human committed megakaryocytic progenitor cells in vitro (CFU-M) synthesize glycoproteins lIb and lIla. Nonadherent light-density human bone marrow cells were cultured in human plasma and methylcellulose using conditions that promote large megakaryocytic colonies. On day i 3 the megakaryocytic colonies were picked. pooled. and pulsed with ThS methionine in methionine-free media. Populations of approximately 1 00,000 cells with >95% viability and containing 70% to 90% megakaryocytes were obtained reliably for study. After the radioactive pulse. the cell suspension was solubilized with nonionic detergent. To reduce nonspecific binding of ThS labeled proteins to agarose, the lysate was chromatographed sequentially on glycine-quenched Affi-gel and antihuman factor X-Sepharose. The unbound material from these resins was then chromatographed on an antiglycoprotein llb/Illa monoclonal antibody resin (HP1 -1 D.-Sepharose) or on a control