Changes in the fibroblastoid colony forming unit population from mouse bone marrow in early stages of Soule virus induced murine leukemia.

Fibroblastoid cells from mouse bone marrow belong to the hemopoietic inductive microenvironment involved in the regulation of hemopoiesis (1). We observed a decline in the incidence of precursors of these cells (fibroblastoid colony forming units) in the early stages of viral leukemogenesis. This was not accompanied by similar changes in bone marrow derived hemopoietic colony forming cell populations (CFU-s and CFU-c). Cultured fibroblastoid colonies from the bone marrow of young AKR mice or Soule murine leukemia virus inoculated BALB/c mice were found to produce type-C ecotropic virus. No such production was observed when similarly cultured granulocyte macrophage colonies (CFU-c) from the bone marrow of these mice were examined. The possibility that the fibroblastoid cell population is a major source of ecotropic leukemia viruses in the early stages of viral leukemogenesis is discussed.