IgA rheumatoid factor and IgA containing immune complexes in primary Sjögren's syndrome.

IgA rheumatoid factor (RF) and immune complexes containing IgA-IgG, C3-IgA, and C3-IgG from sera of patients with primary Sjögren's syndrome and controls were quantified by ELISA. Salivary tissue obtained from patients at the same time as serum was scored to simultaneously reflect lymphoplasmocytic infiltrate and fibrosis. Patients had significantly increased amounts of IgA RF and all complexes when compared to controls (p less than 0.0005). IgA-IgG complexes, thought to be IgG-IgA RF complexes, were inversely correlated to tissue pathology (p less than 0.001) and peripheral white blood cell counts. Additionally, IgA RF was inversely correlated to stimulated parotid flow. This suggests immune complex formation precedes tissue destruction or is associated with less destructive pathology in primary Sjögren's syndrome.