title: Release of granulocyte-macrophage colony-inhibiting activity by normal human postthymic precursor cells.
abstract: Seven normal human peripheral blood cell fractions (buffy coat, mononuclear cells, non-T, T, Fc-IgM receptor-depleted T-lymphocyte, Fc-IgG receptor-depleted T-lymphocyte, and autologous rosette-forming T-cell-depleted T-lymphocyte subpopulations) treated with phytohemagglutinin (PHA) were examined for the production of granulocyte-macrophage colony-stimulating activity (CSA). It was found that medium conditioned by a T-lymphocyte subpopulation depleted of autologous rosette-forming T-cells (Tar cells, a postthymic precursor subpopulation that inhibits Ig synthesis) stimulated colony-forming units of granulocyte and macrophages (CFU-GM) to a greater extent than did the other conditioned media (CM) analyzed. Based on this finding, CM from an enriched Tar subpopulation was prepared and thus showed that PHA-treated Tar cells release a factor capable of inhibiting CFU-GM growth. The inhibitory activity of this factor persisted-after heat inactivation, suggesting that cause of the colony-inhibiting activity (CIA) is other than interferon. Further studies revealed that Tar-derived inhibitory factor acts either directly upon CFU-GM or via monocytes/macrophages (M phi/Ma), enhancing CIA, and not the level of CSA production by M phi/Ma. The overall data are interpreted as demonstrating the presence of CIA in a specific T-lymphocyte subpopulation that may represent a new relationship between lymphocytic and myelocytic systems in the human.
mesh_terms: D003114:Colony-Forming Units Assay; D003115:Colony-Stimulating Factors / Q000378:metabolism; D003470:Culture Media; D006098:Granulocytes / Q000502:physiology*; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008213:Lymphocyte Activation; D008264:Macrophages / Q000502:physiology*; D011506:Proteins / Q000378:metabolism*; D012397:Rosette Formation; D013601:T-Lymphocytes / Q000145:classification / Q000378:metabolism*
chemical_list: D003115:Colony-Stimulating Factors; D003470:Culture Media; D011506:Proteins; C016313:colony inhibiting factor