Presence of pluripotent haemopoietic precursors in vitro (CFU‐mix) in haemopoietic tissues from mice of W/Wv genotype

The presence or absence of haemopoietic precursors, which produce mixed colonies in vitro (CFU-mix) was examined in the bone marrow and spleen of (WB X C57BL/6) F1-W/Wv mice. Despite the failure of macroscopically evident colony-formation in the spleens of irradiated mice, haemopoietic cells of W/Wv mice did produce macroscopically-evident mixed colonies containing erythroid cells, macrophages, and often megakaryocytes, in culture medium. The size and constitution of mixed colonies derived from W/Wv mice were comparable to those of mixed colonies from congenic +/+ mice. The present results appear consistent with in vivo haemopoiesis in the W/Wv mice, which is obviously deficient, but sufficient for survival.