Formation of factor-independent hematopoietic multilineage colonies after Abelson virus infection.

Yolk-sac-derived hematopoietic cells were infected with a helper-free stock of Abelson virus (A-MuLV). After infection, cells were plated in a clonogenic methylcellulose culture in the absence of exogenous growth factors such as interleukin 3 (IL 3) and erythropoietin (Epo). No colonies were observed in cultures without viral infection, whereas factor-independent colonies were consistently observed with virus-infected cultures. The number of colonies was linearly correlated with the number of cells plated. Erythroid-mix colonies consisting mostly of erythroblasts, macrophages, and mast cells could be observed. Tumorigenic, continuously growing mast cell lines could be generated at high frequency from these erythroid-mix colonies after they were initially passaged in the presence of an irradiated feeder layer for 4 to 8 weeks. Southern blot analysis of the DNA from five of these lines examined were all shown to contain integrated A-MuLV proviral DNA. These data are evidence that A-MuLV can directly infect embryonic multipotent hematopoietic progenitor cells and drive them to differentiate to various progeny cells without exogenous growth factors.