Expression of a cross reactive idiotype on the IgG 2c subclass of rat anti-streptococcal carbohydrate antibody

Abstract

Eight inbred rat strains when hyperimmunized with Group A streptococcal vaccine (GASV) produced only low levels (0–1.7 mg/ml) of precipitating anti-streptococcal carbohydrate antibody (anti-SACHO). In contrast, partially inbred Sprague-Dawley-derived rats (HPR) produced in our laboratory make 5–36 mg/ml precipitating anti-SACHO. A high percentage of immunized animals possessed a crossreactive idiotype, Id-1. No correlation was found between Ag-B haplotype or light chain allotype and the expression of Id-1, or the magnitude of the anti-SACHO response in this or our previous studies. Of the animals examined, the total serum IgG 2c increased approximately 93 times over that found in preimmune serum e.g. 0.3 mg/ml pre- to 28.0 mg/ml post-immunization. In contrast the total IgG 2a and IgG 2b and IgM increased ~ 1.7-, 3- and 7-fold, respectively. The hyperimmunoglobulinemia that remains in some immune sera after passage through an N-acetyl glucosamine-containing immunoadsorbant suggests that immunization with GASV induces considerable levels of low-affinity anti-SACHO and/or antibodies with non-SACHO specificities. Specifically purified precipitating IgG anti-SACHO from 6 inbred strains and HPR were almost totally of the IgG 2c subclass. These data suggest that Id-1 is preferentially expressed on IgG 2c anti-SACHO. Furthermore, a discussion of the possible reasons for the selective expression of Id-1 with IgG 2c. is given.