Experimental erythroblastosis fetalis in rabbits. I. Characterization of a pair of allelic blood group factors and their specific immune isoantibodies.

A pair of blood group factors, designated G and g, was identified in rabbits by serological means. These factors were found to be alleles, and one or the other or both of them were regularly present in the red cells of every one of a large number of mongrel and inbred rabbits. The factors were not demonstrable in other tissue cells or in the body fluids. They were capable of stimulating the formation of specific immune isoantibodies when repeatedly injected into appropriate rabbits. In most instance both agglutinating and coating antibodies to the G or g factors were present in a given antiserum. The coating antibodies-which did not act as true blocking antibodies-were detected by means of an antiglobulin test (Coombs test), or by means of specific cells modified by the action of trypsin. The antibodies were heat-stable and were active over a wide temperature range; and under suitable conditions, they proved to be potent hemolysins and also capable of fixing complement. The characteristics of the antigens and antibodies of the rabbit G-g system bear a striking resemblance to those of the Rh-Hr system of man.