Human serum antibodies reactive with dietary proteins. Antigenic specificity.

The antigenic specificity of human serum IgG antibodies reactive with common dietary proteins has been evaluated by competitive binding using a solid-phase immunoassay (ELISA). Antibodies reactive with bovine milk antigens were shown to be reactive predominantly with casein, rather than alpha-lactalbumin, beta-lactoglobulin, gamma-globulin or albumin. Furthermore, sera containing antibodies reactive with bovine casein, wheat gliadin and chicken ovalbumin showed competitive binding only by each respective dietary protein antigen. IgG4 antibodies specifically reactive with ovalbumin, gliadin or casein were also not cross-reactive in competitive binding studies. Furthermore, both IgG2 and IgG4 anti-milk antibodies showed significant inhibition only with bovine casein, and not with alpha-lactalbumin or beta-lactoglobulin. These data are relevant to concepts regarding the immunobiological role of antibodies of the IgG4 isotype.