Studies on Xenopus laevis immunoglobulins.

The anuran amphibian has been shown to produce two classes of antibodies to HGG, BSA and Hc. These antibodies were characterized by gel filtration on Sephadex G-200 as 19S' and 7S' immunoglobulins. In the course of immunization, antibody activity could be initially detected in the 19S' immunoglobulin fraction, followed by the appearance of the activity in the 7S' immunoglobulin fraction at a later stage of immunization. A switch-over from 19S' to 7S' activity was not observed. Both immunoglobulins were composed of heavy and light polypeptide chains. The 19S' protein had heavy chains with a molecular weight of 74,500, similar to human μ-chain (73,900). The 7S' protein differed from human IgG in respect to the molecular weight of its heavy chain which was shown to be 64,500. Light chains of both immunoglobulins of were found to have a molecular weight of 26,700, similar to human immunoglobulin light chains (25,000).