Monoclonal antibodies directed against human Rh antigens in tests with red cells of non-human primates

Human anti-D (Rh_o) monoclonal antibodies (Mabs) of the IgG (70) and IgM (27) classes were tested with red blood cells (RBCs) of various non-human primates, from anthropoid apes to New World monkeys. Significant differences in reactivity were observed among antibodies of two classes depending on taxonomic position of primate animals. Only IgM Mabs gave positive reactions (9 out of 18 Mabs) with blood of Old World monkeys. Allotypic reactions with RBCs of African apes were produced by a majority of IgG Mabs but by very few IgM reagents, most of the latter reacting with RBCs of all chimpanzees and all gorillas tested. Eight out of 70 IgG anti-D defined chimpanzee polymorphisms related to chimpanzee R^c antigen which is the chimpanzee counterpart of human D antigen. Most of IgG anti-D Mabs (61/70) were found specific of D^gor antigen (gorilla counterpart of human antigen D). Most of anti-D which were found negative with all chimpanzee RBCs were also negative with human D^IVb RBCs and most of anti-D which agglutinated human D^IVb RBCs were positive with some or all chimpanzee blood samples. Differences among Mabs evidenced in tests with non-human primate RBCs reflect the complexity of the immune reactions to the human D antigen. The results obtained with anti-Rh Mabs of specificities other than D confirmed that chimpanzee, gorilla and gibbon express c-like epitopes and that antigens C, E, e are absent in non-human primates.