Normal and Friend virus specific cell compartments in Friend leukemia characterized by their sensitivity to actinomycin D in vivo.

DBA/2 mice were infected with the polycythemia inducing Friend Virus (F-MuLV-P) and treated with different doses of Actinomycin D (Act D) when the whole erythroid cell system, as measured by the CFU-E technique with and without addition of erythropoietin (Ep), had been transformed into Ep-independence. During and after this therapy the different stem cell pools CFU-S, CFU-C, BFU-E and CFU-E (with and without Ep) were studied and their sensitivity to Act D in bone marrow and spleen was compared to that of normal mice, recently published by other authors. There seemed to be no difference in the Act D sensitivity between normal erythropoiesis and Ep-independent erythropoiesis caused by F-MuLV-P. Furthermore a cell called ICPC (infectious centers producing cell) was studied. This cell system, detected by spleen colony formation due to high local virus production in an unirradiated host, proved to be Act D sensitive in the spleen but not in the marrow. When the erythroid cell system regenerated after Act D chemotherapy, all erythroid colony growth was Ep-independent. This means that Act D did not induce normal erythropoiesis as seen with hydroxyurea treatment.