Knowledge of blood groups and blood types is important in making transfusion decisions. Blood group data have also been used by evolutionary biologists to measure genetic distances between populations. No studies have examined blood groups in elephants. Whole blood and serum from 41 Asian elephants (Elephas maximus) with no previous transfusion history were evaluated using a standard crossmatch tube agglutination test with a 15 min incubation at 37°C. A positive crossmatch with at least two other elephants occurred in 73% of the elephants tested, suggesting that Asian elephants have natural occurring agglutinating antibody to blood types they do not themselves demonstrate.
The same 41 elephants were also evaluated for warm agglutinating antibody to erythrocyte antigens by tube agglutination. One elephant demonstrated evidence of an antibody against a high incidence antigen present on 80% of erythrocytes. Seven other antibodies were identified that showed reactivity to 20% of the erythrocytes tested. To demonstrate that antigenicity was erythrocyte-based, adsorption studies were performed. Crossmatch reactivity was successfully removed from serum by adsorbing the serum to red blood cells carrying the corresponding antigen. The elephant described above required two different and separate adsorptions to remove all reactivity, suggesting either that elephants blood types may involve more than one blood group or that the red blood cells of some elephants bear multiple antigens.
Although the in vivo reactivity of these erythrocyte antigens is unknown, these findings suggest that elephants need to be crossmatched prior to whole blood transfusion. Additional characterization of these antigens and antibodies are underway.