Medium conditioned in the presence of human HUT-102 T-cell line cells contains activities stimulating human mixed (colony-forming unit, erythroid, granulocyte, macrophage, megakaryocyte) and erythroid (burst-forming unit, erythroid) colony formation in methylcellulose in vitro and granulocyte colony formation in diffusion chambers in mice. The stimulatory effect of HUT-102-conditioned medium on colony-forming unit, granulocyte diffusion chamber was also observed in diffusion chambers implanted

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... n nude mice. The hemopoietic activities were heat stable and could be detected from serum-free conditioned medium. Chromatographically, it was possible to separate colony-forming unit, granulocyte diffusion chamber-stimulating activity from activities stimulating burst-forming unit, erythroid and colony-forming unit, erythroid, granulocyte, macrophage, megakaryocyte. On the other hand, the latter two activities were indistinguishable by the methodology used in this study. Failure to abolish the hemopoietic activities by boiling or by human T-lymphotropic retrovirus type 1 antibody indicates that human T-lymphotropic retrovirus type 1 or its components potentially present in the conditioned medium were not responsible for the stimulatory effects.