IgG subclass antibodies to dietary antigens in IgA deficiency quantification and correlation with serum IgG subclass levels.

IgG subclasses of antibodies to the dietary antigens ovalbumin, beta-lactoglobulin, casein, bovine IgM, and glycgli (a gluten component) were quantified in 20 adults and 10 children with IgA deficiency and healthy controls (21 adults and 7 children). In the IgA-deficient subjects the levels of IgG subclasses in serum were determined. Detectable antibody levels were observed in the majority of the subjects in IgG1 and IgG4 for anti-ovalbumin and beta-lactoglobulin, and in IgG1, followed by IgG2, IgG3, and IgG4 for antibodies to casein, bovine IgM, and glycgli. Levels of IgG1 and IgG2 antibodies to bovine IgM were higher in the IgA-deficient adults than in controls (P less than 0.00005, P = 0.0007, respectively), whereas the other antibody levels did not differ significantly between the two groups. An analysis of correlation between the IgG subclass antibody levels did not provide evidence for a particular IgG subclass antibody response pattern against different protein antigens within the single individual. Serum IgG4 levels correlated positively with the summed IgG4 antibody levels (Spearman's p = 0.673, P = 0.0051). The IgA-deficient subjects, when compared with healthy controls, did not show a particular IgG subclass pattern or restriction of antibodies to dietary antigens.