Epitopes recognized by serum anti-α-galactoside antibody are present on brain glycoproteins in man

Naturally occurring serum IgG against terminal α-galactoside epitopes (anti-Gal), present exclusively in man, apes and old world monkeys, was used as probe for these epitopes in human brain. Human brain grey matter soluble glycoproteins enriched inα galactosyl groups by affinity chromatography on jacalin-sepharose, specifically binds to human anti-Gal in immuno dot blots. Anti-Gal recognized exclusively the terminal α galactoside epitope in human brain glycoproteins since binding was abolished by the presence of 1-0-methyl α-D-galactopyranoside as well as by pretreatment of glycoproteins with coffee bean α-galactosidase. Anti-Gal-peroxidase staining of jacalin-binding human brain glycoproteins in western immuno blots revealed mainly five anti-Gal-binding polypeptides withM _r (in kDa) of 94, 108, 180, 210 and 230 respectively. Since the presence of anti-Gal in higher animals accompanies suppression of the corresponding epitope in most tissues, apparently to maintain immunological balance, possible implications of the above observation for autoimmunity, tumor metastasis and infection are discussed.