Human T-lymphocyte-derived megakaryocyte colony-stimulating activity.

Conditioned medium from a T-lymphoblastic cell line (Mo) contains a number of well-characterized hemopoietins. In this paper we demonstrate that Mo cells also release a factor(s) able to stimulate the growth and the differentiation of megakaryocytic progenitors into large-size pure megakaryocytic colonies in plasma clot cultures. Comparison with other sources of human-active hemopoietins shows that Mo-conditioned medium performs better than others, especially for the megakaryocytic lineage. The factor(s) shows strong similarities with human Meg-CSF obtained from a thrombocytopenic patient's plasma, and is distinguishable from the other hemopoietins present in the medium.