Colony formation by primitive hemopoietic progenitor cells in serum-free medium.

A serum-free medium has been developed for clonal growth of murine hemopoietic progenitor cells. In this medium, the number of nonerythroid colonies induced by factors produced by cloned T lymphocytes was 90 +/- 10% of the number generated in serum-containing medium. Erythroid colony number in serum-free cultures containing the T-cell factors but no exogenous erythropoietin was significantly higher than that in cultures with serum, and the cloning efficiency was independent of cell concentration. Further addition of erythropoietin increased erythroid colony number approximately equal to 4-fold. Pure erythropoietin alone stimulated erythroid colony formation, but the cloning efficiency was highly dependent on cell concentration. Analysis of individual colonies generated in serum-free cultures containing the T-cell factors indicated that some contained cells of several hemopoietic lineages, demonstrating that multipotential progenitors can give rise to colonies in this system.