Phylogeny of immunoglobulin structure and function XV. Idiotypic analysis of shark antibodies.

Nurse shark antibodies to the streptococcal A-variant carbohydrate were specifically purified from the sera of four individual animals and used as immunogens in guinea pigs. The resultant guinea pig antisera contained antibodies with apparent idiotypic specificities for the homologous shark proteins. The shark idiotypic sites were located on the Fab fragments and appeared to require the participation of H and L chains for full expression. Tests for cross reactivity employing the four guinea pig anti-idiotypic sera and antibodies from 13 immunized sharks were positive in only two cases (heterologous inhibition). These findings indicate that the idiotypic library (and by inference the antibody combining site repertoire) of nurse sharks to the streptococcal A-variant antigen is probably quite extensive.