Differences between Populations of Fresh Water Catfish Defined by Blood Group Antigens and Antibodies

The presence of cross-reacting hemagglutinins in fresh water catfish maintained under laboratory conditions enabled a classification of the fish into two distinct groups. The erythrocytes and serum from groups I and II used as reagents in testing other individuals permitted similar distinctions in catfish obtained from several different sources. The agglutinogen in erythrocytes from group I individuals was A-like in nature, based upon agglutination studies using lima bean lectin and human anti-A hemagglutinins; it also possessed Forssman-like activity as inferred from differential absorption studies using guinea pig kidney and bovine erythrocytes. The demonstration that hemagglutinins in group II sera were highly cross-reactive with human erythrocytes, including A1 and A1B, thus suggested a basis for interactions with group I red cells. The basis for a reciprocal effect, namely agglutination of group II cells by group I sera, was less clear, but may be related to the widespread reactivity of these sera against all human erythrocytes tested.