Characterization of stimulatory activity for human pluripotent stem cells (CFUGEMM).

A medium conditioned by leukocytes in the presence of phytohemagglutinin (PHA-LCM) promotes the growth of human multilineage hemopoietic progenitors CFUGEMM which form mixed hemopoietic colonies in culture containing granulocytes, erythroblasts, megakaryocytes, macrophages and mononuclear cells with T-cell antigens. In addition PHA-LCM supports the growth of erythroid bursts (BFUE) and granulocytic colonies (CFUC). Stimulatory activities of PHA-LCM were characterized by gel filtration using Sephacryl S 300. The eluted growth promoting activities were rechromatographed on Sepharose 4 B covalently linked with Lentil Lectin. The stimulatory activities for noncommitted precursors CFUGEMM, and committed progenitors BFUE, and CFUC were detected in the unretained material i.e. the activities revealed no affinity to Lentil-Lectin. The apparent molecular weight of these stimulatory molecules ranged from 35,000-45,000, as determined by SDS gel electrophoresis (PAGE).