Different Ia antigen characterization between granulocyte progenitor cells (CFC-G) and monocyte―macrophage progenitor cells (CFC-M)

: Ia-like antigen-positive (Ia+) and -negative (Ia-) cell populations were separated from human cord blood cells and bone marrow mononuclear cells by a rosette technique with a combined use of staphylococcal protein-A-coated bovine red blood cells and the monoclonal OKIa 1 antibody, or by using a cell-sorting technique. Colony-forming units-granulocytes-monocytes-macrophages (GFU-GM) were assayed in a semisolid agar culture, and colony-forming cells-granulocytes (CFC-G) were differentiated from colony-forming cells-monocytes-macrophages (CFC-M) by double staining for esterase activity. The majority of CFC-G in cord blood was grown in the Ia+ fraction; Ia+ CFC-G/Ia- CFC-G = 1.62 +/- 0.34 (mean +/- SD), which was similar to the ratio in bone marrow (Ia+/Ia- = 1.80 +/- 0.37). In contrast, the majority of CFC-M in cord blood was grown in the Ia- fraction; Ia+/Ia- for CFC-M = 0.50 +/- 0.09. The predominance of CFC-G in the Ia+ fraction in contrast to predominance of CFC-M in the Ia- fraction was confirmed by using a cell-sorting technique. T-lymphocyte depletion and the culture supernatants of Ia+ and Ia- cells did not affect differentiation of CFC-G and CFC-M. These data suggest that there are potent differences in the expression of Ia-like antigens between CFC-G and CFC-M, indicating that the Ia+ progenitor cell population generates predominantly CFC-G, whereas the Ia- population generates mainly CFC-M during the maturation process in granulopoiesis.