Pulmonary and extrapulmonary sarcoidosis in relation to circulating immune complexes: a quantification of immune complexes by two radioimmunoassays.

Serum specimens from 53 patients with pulmonary sarcoidosis were examined for the presence of immune complexes by 2 methods, the Raji cell and the monoclonal rheumatoid factor radioimmunoassays. We found increased concentrations of immune complexes in the sera of 27 patients by one or both techniques. A significant association was found between increased concentrations of immune complexes and stage III sarcoidosis. Seventeen of 23 patients with stage III sarcoidosis and 10 of 50 with stage I or II disease had increased concentrations of immune complexes. Eight of the 10 patients with stage I or II sarcoidosis and increased concentrations of immune complexes had extrapulmonary sarcoid features, such as erythema nodosum, synovitis, or salivary gland enlargements. The size of the immune complex was 15S in one of the patients examined. Concentrations of C4 were normal. The data suggest a possible role of immune complexes in the pathogenesis of pulmonary and extrapulmonary features of sarcoidosis.