Analysis of the gastrointestinal secretory immune barrier in IgA deficiency.

Secretory IgA is known to play a major role in the exclusion of foreign antigens from the systemic compartments. We have previously shown that IgA-deficient subjects can have large amounts of circulating immune complexes containing bovine antigens of dietary origin, presumably due to the defective secretory barrier. In these studies, we investigated whether the peak amount of immune complexes found after specific antigen challenge could be related to the level of serum or salivary IgA. Our data show that the peak of immune complex is not related to either serum or salivary IgA but that it is closely correlated to the titer of antibody to milk proteins. In addition, it appears that some individuals with only modest IgA deficits can have substantial mucosal permeability defects on milk challenge.