Differential expression of Qa-m2 alloantigen on murine hemopoietic progenitor cells. Selective enrichment for megakaryocyte progenitors.

The selective expression of Qa-m2 antigen on murine megakaryocyte colony-forming cells (MEG-CFC) has been demonstrated. A monoclonal antibody defining the Qa-m2 alloantigen has been shown to inhibit, in the presence of complement, in vitro formation by murine bone marrow cells of megakaryocyte colonies, but not granulocyte-macrophage, erythroid or eosinophil colonies. Inhibition of megakaryocyte colony formation was shown, by mixing and other experiments, to be due to C-mediated lysis of MEG-CFC rather than lysis of accessory cells. B-lymphocyte colony formation was reproducibly decreased by approximately 50%, demonstrating the presence of Qa-m2+ and Qa-m2- subsets of B-lymphocyte colony-forming cells (BL-CFC). MEG-CFC and granulocyte-macrophage colony-forming cells (GM-CFC) were also found to be Thy-1-, Ly-1-, Ly-6- and Ly-5-. Fractionation of Thy-1-, Ig- marrow by rosetting Qa-m2+ cells and centrifuging them through an Isopaque-Ficoll gradient yielded up to 8-fold enrichment for MEG-CFC and greater than 20-fold separation of MEG-CFC from GM-CFC. The anti-Qa-m2 antibody should be useful for further purification of MEG-CFC, and investigation of hemopoietic differentiation.