Erythropoiesis in Friend leukemia: red blood cell survival and ferrokinetics.

The Friend virus causes a leukemia characterized by the early development of thrombocytopenia in the peripheral blood and by reticulum cell and erythroid hyperplasia in the spleen (6,8-11). Significant thrombocytopenia occurs 2 days after infection and is a major factor in the hemorrhagic disorder that results in the early death of affected animals (6). Approximately 3-4 days after infection, enlarging foci of reticulum cells surrounded by ac cumulations of erythroblasts in all stages of development are evident on histologie examination of the spleen (11). The rela tionship of these erythroid elements to the reticulum cells is not clear (11). Ludwig et al. (10) postulated that the altered erythro poiesis in Friend leukemia could be secondary to either hemolysis with a compensatory increase in erythropoiesis or the induction of an erythroleukemia by the Friend virus. On the basis of their pathologic studies in BALB/c and RF mice they suggested that the Friend virus caused erythroleukemia (10). However, Metcalf et al. (11), from theirpathologie studies, concluded that the altered erythropoiesis was benign and not a form of erythroleukemia. In the study reported herein, the survival of RBC from Friendinfected and normal mice was studied by means of noncohort labeling with radioactive chromium (51Cr) and cohort labeling with radioactive iron (^Fe). Studies were performed in both non splenectomized and splenectomized mice. Ferrokinetic studies, including the MFeij, the plasma iron turnover, the reappearance of MFein the RBC and, the uptake of 59Fein the spleen, were ob tained in control and infected mice. The data in this study incli-