Catfish antibodies to blood group substances. 3. Further studies with sera from fish injected with human group O secretor fluids.

An antiserum prepared in the freshwater catfish by the injection of O secretor seminal plasma was fractionated into anti-H reagents showing different specificities by absorption with AB erythrocytes and by absorption and elution from AB cells. Although purified human and hog H blood group substances inhibited the haemagglutination of O erythrocytes by both the eluate from AB cells and the serum remaining after absorption with AB cells, all of the simple sugars tested, except 2′-fucosyl-lactose, failed to inhibit either sample. The H-substances inhibited the AB-eluate at dilutions which were significantly higher than those required to inhibit the AB-absorbed serum. Inconsistent with this result was the finding that 2′-fucosyl-lactose, a trisaccharide with a structure similar to the terminal H-active groupings on the type 2 chains of the ABH macromolecules, was a more active inhibitor of the absorbed than of the eluted serum. Seventeen different samples of O secretor saliva either failed to inhibit the AB-absorbed serum, or produced inhibition at very low dilution. These same saliva samples inhibited the AB-eluate in high dilution.