Presence of cells in B-cell lineage in mixed (GEMM) colonies from murine marrow cells

Recent progress in clonal cell culture techniques makes it possible to detect pluripotent hemopoietic precursors from murine marrow cells. The precursors can proliferate, differentiate and form mixed colonies containing erythroblasts, granulocytes, macrophages and often megakaryocytes in viscid culture medium. In the present investigation, the presence of cells of B-cell lineage in mixed colonies was investigated. Experiments on colonies containing cIgM, cIgG, sIgM and sIgG bearing cells using goat IgG fluorescein-conjugated anti-mouse IgM, goat F(ab')2 fraction fluorescein-conjugated anti-mouse IgG and immunobeads revealed the presence of cytoplasmic IgM bearing cells in 47% of the colonies and surface IgM bearing cells in 74-84% of the colonies. Mixed colonies, however, did not contain either cIgG bearing cells or sIgG bearing cells. The results may indicate that some CFU-MIX proliferate and differentiate along B-cell lineage to sIgM or cIgM bearing cells in vitro.