Circulating immune complexes in IgA deficiency.

Circulating immune complexes (IC) were demonstrated in patients with serum IgA deficiency. Sixteen of thirty-one IgA deficient patients had serum IC detected by solid phase C1q radioimmunoassay for IgG class complexes. The presence of cryoglobulins (thirteen out of thirty-one patients) and increased polyethylene glycol precipitation (ten out of thirty patients) provided additional evidence for the presence of IC. Fourteen patients were asymptomatic but seven had clinical evidence of disease which could have been IC mediated: two with glomerulonephritis, three with polyarthritis, one with vasculitis and one with thyroiditis. Serum IC remained detectable in multiple samples over several months but this correlated poorly with the presence or absence of disease. Serum antibody to IgA was detected in fifteen out of thirty-one patients. There was no direct relationship between the presence of IC and the level of serum anti-IgA antibody; however, this antibody was shown to be present in the IC isolate in eight patients. It is proposed that a considerable portion of the IC load in IgA deficiency results from defective antigen exclusion at the level of the mucosa.