ISOLATION OF A MURINE BONE-MARROW CELL-LINE PRODUCING A NOVEL ERYTHROID-ENHANCING ACTIVITY

Erythroid differentiation requires hematopoietic factors to proceed fr om early erythroid progenitors, burst-forming units-erythroid (BFU-E), to mature red cells. A number of factors possessing burst-promoting a ctivity (BPA) have been characterized, such as interleukin-3 (IL-3), s tem cell factor (SCF), and granulocyte-macrophage colony-stimulating f actor (GM-CSF). These factors have broad spectra of activity on differ ent hematopoietic and nonhematopoietic cell lines. In this paper, we d escribe the effect of an apparently selective erythroid factor that ac ts on a class of mature BFU-E, giving rise to bursts containing a rela tively small number of subcolonies. This activity is produced by a bon e marrow cell line; it is a glycoprotein, since it is destroyed by pro teases; it is retained on Concanavalin A/Sepharose; and it precipitate s at low ammonium sulfate concentration, indicating high hydrophobicit y. This activity, shown to be different from known hematopoietic cytok ines having BPA, exhibits an apparent strict erythroid specificity. Si nce it increases the development of rather small bursts probably arisi ng from mature BFU-E, we refer to it as murine burst maturation promot ing activity (mBMPA).