title: Differential expression of Ia molecules by human monocytes.
abstract: Human immune response genes can be divided into three distinct loci, each of which codes for three distinct families of Ia molecules: HLA-SB, HLA-DC, and HLA-DR. The tissue distribution and function of only one of these Ia molecules, HLA-DR, has been thoroughly studied. Using monoclonal antibodies, we examined the display of HLA-DR and HLA-DC molecules by adherent, human peripheral blood monocytes. The results of these studies demonstrate that although all human peripheral blood monocytes display easily detectable HLA-DR molecules, only 50% display easily detectable HLA-DC molecules. Separation of peripheral blood monocytes into HLA-DC+ and HLA-DC- cells demonstrates that each population displays an equivalent density of HLA-DR molecules. Therefore, on the basis of differences in their display of these two Ia molecules, adherent peripheral blood monocytes can be divided into two broad populations: HLA-DR+, HLA-DC+, and HLA-DR+, HLA-DC-. Despite the dis-coordinate display of these Ia antigens, the expression of both HLA-DR and HLA-DC can be regulated by a common signal, gamma interferon (IFN-gamma). Incubation of monocytes for 96 h in autologous serum leads to a marked decrease in the expression of both HLA-DR and HLA-DC. Addition of recombinant IFN-gamma to the cultures leads to reexpression of both HLA-DR and HLA-DC to levels comparable to those seen in fresh monocytes. In addition, although IFN-gamma does not modulate all monocyte surface markers, it can be demonstrated to modulate expression of one marker, MAC 120, in a manner similar to that observed for Ia antigens. These studies demonstrate that among human peripheral blood monocytes, the distribution of the Ia molecule, HLA-DC, is not coordinate with that of HLA-DR, although both respond to the same regulatory signal.
mesh_terms: D000911:Antibodies, Monoclonal; D002478:Cells, Cultured; D005802:Genes, MHC Class II; D006680:HLA Antigens / Q000235:genetics*; D006682:HLA-DP Antigens; D006683:HLA-DQ Antigens; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II / Q000032:analysis*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D006680:HLA Antigens; D006682:HLA-DP Antigens; D006683:HLA-DQ Antigens; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D007371:Interferon-gamma