Circulating immune complexes in sarcoidosis

Abstract

The sera of 50 patients with sarcoidosis were tested for the presence of circulating immune complexes using polyethylene glycol precipitation, followed by single radial immunodiffusion for the amounts of C1q, IgG, IgM, and double diffusion for the presence of IgA. Complexes were detected in 29 (58%) patients. No correlation could be found between the presence of these complexes and the length of history, stage, or activity of disease, nor to steroid therapy. Rheumatoid factor was detected in 14 patients (28%), 13 of whom had circulating immune complexes, and 12 of whom had active disease. Total serum C3, CH50, and C1q were normal, as were immunoglobulin levels. In patients with extrathoracic sarcoidosis, especially skin or joint involvement, complexes were commonly found. The aetiological significance of these complexes remains uncertain.