INHIBITORY EFFECTS OF INTERFERON ON MOUSE MEGAKARYOCYTIC PROGENITOR CELLS IN CULTURE

Abstract

Mouse bone marrow cells were grown in plasma clots and megakaryocyte formation was stimulated with human urinary erythropoietin (Ep). The expression of megakaryocyte colony forming units (CFUM) and of single megakaryocyte forming units (M) was evaluated after 7 days in culture. Usually 10 times more M than CFUM were found. Megakaryocytic colony formation showed a linear dependence on cell dose from 0.5 to 2 .times. 105 cells/clot. The colony size frequency distribution exhibited a single peak in the 2-cell size class, followed by a continuous decrease, suggesting that cell division may occur asynchronously in cells making up a colony. Mouse [neoplastic fibroblast] L cell interferon (IF) in doses from 10-1000 U/ml was included in clots together with Ep. This resulted in a biphasic, dose-dependent reduction of colony formation and of single megakaryocyte formation. At all doses tested, CFUM were more sensitive to IF than M. These observations are best explained by a differential inhibitory effect of IF on replication of 2 or more classes of megakaryocytic progenitor cells.