Identification of a cold agglutinin with anti-Pr3 specificity

An apparent monoclonal IgM, kappa-cold agglutinin with anti-Pr specificity was detected in the serum of a 38-year old woman. Haemagglutination inhibition studies disclosed the subspecificity anti-Pr3, since the cold agglutinin was strongly inhibited by carbodiimide-treated erythrocyte glycoproteins. Studies with animal cells showed that the corresponding Pr3 determinant was found only on human red cells. This is in contrast to earlier findings and indicates that distinct fine specificities within anti-Pr3 antibodies might well exist.