The immune response to bloodgroup substances

Abstract

Guinea pigs were immunized with purified human A and Le^a blood-group substances. Skin testing revealed a delayed hypersensitivity response to A and Le^a and other human blood-group substances, showing a very marked degree of cross-reactivity, irrespective of the immunizing antigen. Circulating antibody was tested for by eliciting systemic anaphylaxis, by direct cutaneous anaphylaxis using a dye-spreading method, and by the passive cutaneous anaphylaxis test of Ovary. Precipitation and red-cell agglutination tests were also employed. It was found that immunization with A substance consistently produced a major specific anti-A antibody and a minor separate antibody specific for Le^a. Immunization with Le^a substance did not consistently give rise to detectable circulating antibody. In those animals, however, in which antibody to Le^a was found, a reaction with A substance could also be shown. These results could be explained in terms of a small amount of Le^a activity in A substance, as revealed by agglutination-inhibition and P.C.A. tests.

The results indicate that the polypeptide part of blood-group mucopolysaccharides is the entity chiefly concerned in producing and eliciting delayed hypersensitivity to these substances. The cross-reactivity of the delayed response supports the view that the different human blood-group mucopolysaccharides share a similar polypeptide component.

The more precise nature of the circulating antibody is explicable in terms of a response to the specific polysaccharide entity of blood-group substances. These findings are considered in the light of previous work on the relationship of delayed hypersensitivity to the circulating antibody response. The question of a possible delayed response to carbohydrate antigen is left unanswered.