Systemic immunization against IgA in immunoglobulin deficiency.

The presence of serum IgM and IgG antibodies against IgA is common among individuals with IgA deficiency. The route of immunization is still unknown, but it is possible that immunization occurs through the gut. We analysed anti-IgA antibody production in gastrointestinal lavage, saliva and breast milk from patients with IgA deficiency. In no case was there any evidence of local production of anti-IgA antibodies. Immunization may thus be due to exposure to endogenous IgA and therefore represent a 'true' autoimmune phenomenon which may possibly be involved in the pathogenesis of the disease.