title: Human myeloid precursors forming colonies in diffusion chambers expresses the Ia-like antigen.
abstract: Normal human bone marrow contains cells capable of forming myeloid colonies (CFU-DG) in fibrin clots in diffusion chambers placed in the peritoneal cavity of cyclophosphamide-treated mice. Evidence has accumulated indicating that these colony-forming cells represent an earlier stem cell than the granulocyte-monocyte precursor cell (CFU-C) assayed in soft agar. We provide data showing that these stem cells express the "Ia-like" or DR antigen. In the presence of rabbit Ia antiserum at a titer of 1:300, all CFU-DG were inhibited. Cytotoxicity was complement-dependent. Data are also presented that suggest that the megakaryocyte stem cell also expresses the Ia antigen.
mesh_terms: D000042:Absorption; D000818:Animals; D001854:Bone Marrow Cells; D003114:Colony-Forming Units Assay; D003165:Complement System Proteins / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D006412:Hematopoietic Stem Cells / Q000276:immunology; D006649:Histocompatibility Antigens; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D011817:Rabbits; D013997:Time Factors
chemical_list: D006649:Histocompatibility Antigens; D007106:Immune Sera; D003165:Complement System Proteins