Naturally occurring autologous anti-idiotypic antibodies. Participation in immune complex formation in selective IgA deficiency.

Abstract

Of individuals with selective IgA deficiency, 50% have high serum titers of antibody to bovine proteins and high levels of circulating immune complexes that contain bovine antigens. Because, in animal studies, immunization with antigen-antibody complexes is a very effective means of producing anti-idiotypic antibodies, such autoantibodies were sought in 2 sera known to have large amounts of anti-casein. After IgG isolation and 2-stage affinity chromatography, IgG-like material (MW of H and L chains on sodium dodecyl sulfate-polyacrylamide gel electrophoresis), with binding activity for the F(ab'')2 of anti-casein were isolated from both sera. Pooled human .gamma.-globulin or IgG myeloma proteins did not inhibit binding of specific anti-anti-caseins to the corresponding anti-casein but sodium caseinate did block this binding (by 80 and 95%), indicating that most of these autoantibodies have affinity for the casein-binding site. Naturally occurring anti-idiotypic antibodies have been difficult to conclusively demonstrate in human sera; consequently, these experiments provide evidence of a unique model which may be used to explore the network theory of Ig regulation in humans.