Abstract: | ![]() The concentration of committed granulocytic progenitor cells (CFU-C) in functionally unique subpopulations of human peripheral blood mononuclear cells has been determined by the in vitro methyl-cellulose assay. Using immunoabsorbent column chromatography and rosette-depletion techniques, we have demonstrated that CFU-C, although not present in either purified T or B lymphocyte populations, are highly concentrated in the "null" cell population, which lacks sheep erythrocyte receptors and surface immunoglobulin. Further fractionation of this null subset has demonstrated that CFU-C do not bear complement receptors, but require the presence of peripheral blood mononuclear cell feeder layers for maximum proliferation. |