Autoantibodies against bromelainized mouse erythrocyte: strain distribution of serum idiotype expression and relative peritoneal cell activity

Previously, we demonstrated that the naturally occurring mouse autoantibodies directed against bromelainized mouse red blood cells (BrMRBC) comprised a family of structurally related molecules bearing a common idiotypic determinant (CP) based on structural and idiotypic analysis of a series of anti-BrMRBC monoclonal autoantibodies derived from a fusion of peritoneal cells (PerC) with plasmacytomas. In the present studies, we have evaluated the quantitative expression of circulating CP idiotype related to autoantibodies against BrMRBC in relation to specific PerC anti-BrMRBC plaque-forming activity in an individual mouse of different strains. The data presented here show no direct relationship between serum CP idiotype expression and PerC anti-BrMRBC plaque-forming activity in an individual mouse of all strains tested. However, the circulating CP idiotype content is higher in strains, viz., CBA/J, NZB, C3H, BXSB, and Biozzi high responder (H) mice which exhibit a high perC autoantibody secretory activity against BrMRBC. The strains such as BALB/c, DBA2, SJL/J, CBA/N, and Biozzi low responder (L) express little or no circulating CP idiotype with a corresponding small or no PerC anti-BrMRBC activity. Furthermore, the PerC "auto"-immune phenomenon is markedly expressed in the normal CBA/J strain since these mice show a higher percentage ratio of CP idiotype over serum IgM (2.68%) as well as highest PerC anti-BrMRBC plaque-forming activity (11,319 +/- 18,029 plaques per million viable cells) compared to other normal and autoimmune strains tested. Nevertheless, the highest circulating serum CP idiotype (49.4 micrograms/ml) is observed in the autoimmune NZB mouse. The immunodeficient CBA/N mice fail to express detectable levels of CP idiotype in their serum. The experiments conducted in genetically selected outbred Biozzi (H and L) strain have revealed remarkable differences in serum CP idiotype expression as well as PerC anti-BrMRBC plaque-forming activity in these two lines. The expression of mouse PerC "auto"-immune phenomenon and quantitative circulation of CP idiotype in the serum seem to be related to regulatory mechanisms as for sheep erythrocytes and other natural antigens earlier demonstrated to be under polygenic regulation in Biozzi (H and L) mice.