Isolation and hemagglutinating activities of bovine immunoglobulins reactive with melibiose

Calcium-dependent and -independent bovine immunoglobulins (IgM and IgG) reactive with melibiose were isolated by affinity chromatography on melibiose-coupled Sepharose 4B. Hemagglutination and hemagglutination inhibition were carried out to study their carbohydrate specificities. Human and animal erythrocytes were agglutinated by these bovine IgM, whereas those were not by bovine IgG at the highest concentrations used. Neuraminidase- and pronase-treated erythrocytes were more strongly agglutinated by these IgM than untreated ones. On the other hand, melibiose-reactive human immunoglobulins isolated from AB serum showed strong hemagglutinating activities to rabbit erythrocytes. Hemagglutination of neuraminidase-treated human type B erythrocytes by calcium-independent bovine IgM reactive with melibiose was effectively inhibited by galactose, methyl alpha-D-galactopyranoside and melibiose, whereas that was not by methyl beta-D-galactopyranoside, lactose, and other substances at the highest concentrations used. Similar results were also obtained in hemagglutination inhibition with untreated rabbit erythrocytes and calcium-independent human immunoglobulins (IgM and IgG) reactive with melibiose. However, hemagglutination of pronase-treated human type A erythrocytes by calcium-dependent bovine IgM reactive with melibiose was not at all inhibited by these substances at the highest concentrations used. From these results, bovine serum is found to also contain antibodies with a specificity for alpha-linked galactosyl residues as found for human AB serum reported previously.