Inhibition of normal erythropoiesis in mice with Friend virus induced erythroleukemia.

Mice in which erythroleukemia was induced by the Friend murine leukemia virus produced inhibitors of normal erythropoiesis. The inhibitors were released into media conditioned by bone marrow cells from leukemic, but not normal mice. The inhibitors were active at high dilution against normal erythroid progenitors (CFUE) in S-phase. Colony formation by CFUE from leukemic mice was stimulated by the same preparations of inhibitor. Fractionation of inhibitory media by gel filtration chromatography revealed 2 protease-sensitive, macromolecular components and a small molecular weight species. The cells responsible for production of the CFUE inhibitors were adherent, possessed macrophage but not T or B cell markers, and did not express viral antigens. The CFUE inhibitors were distinguishable from the previously described inhibitor of granulocyte-macrophage precursors, CFUC LIA, by antigenic specificity and cellular origin.