Immunoglobulins in ranid frogs and tadpoles

Three distinct immunoglobulins (Igs) have been isolated from serum of Rana catesbeiana frogs. One of these is high in molecular weight and probably corresponds to the IgM-like Igs that have been isolated from a variety of vertebrate species. The other 2 Igs are lower in molecular weight (approximately 7S) and very similar in subunit structure. They were highly cross-reactive, although each contained unique antigenic determinants. Their relationship to other vertebrate Ig classes remains to be established. The mode of subunit linkage in all 3 Igs is unusual since the unreduced proteins were partially dissociated in detergent. Serum from R. catesbeiana tadpoles contained Igs that were antigenically identical to each of the Igs in adults of this species. Sera from R. pipiens and R. clamitans frogs and tadpoles contained Igs that cross-reacted with the R. catesbeiana high and low molecular weight Igs.