Reactions of monoclonal antibodies to human MN blood groups with red blood cells of subhuman primates

All 12 samples of chimpanzee erythrocytes tested were agglutinated by the commercial polyclonal anti-M reagent of rabbit origin, but none was agglutinated by monoclonal anti-M reagent of murine origin. This, as well as results of absorption experiments, showed that the polyclonal and monoclonal anti-M reagents detect different M epitopes. Polyclonal anti-N reagent of rabbit origin and monoclonal reagent of murine origin obtained by immunization with N blood group substance did not react with any chimpanzee erythrocyte samples. On the other hand, monoclonal anti-N reagent originating from immunization with M blood group substance agglutinated two of the 12 tested chimpanzee erythrocyte samples. This and other experimental results strongly suggested that the latter monoclonal anti-N reagent combined with "N" antigen, i.e., an antigen present on glycophorin B of human M as well as N erythrocytes; apparently erythrocytes of some chimpanzees contain also this antigen.