Specificity and class distribution of Fc gamma R-specific autoantibodies in patients with autoimmune disease.

To investigate the prevalence of autoantibodies directed against Fc gamma RII (CD32) and Fc gamma RIII (CD16), 151 serum samples from patients with different autoimmune diseases and 25 samples obtained from healthy individuals were assayed by ELISA on microtiter plates coated with recombinant truncated Fc gamma RII and Fc gamma RIII protein. Class specificity was defined with anti-IgG, anti-IgM, and anti-IgA reagents. High titers of circulating IgM autoantibodies reacting with both Fc gamma RII and Fc gamma RIII were characteristic for SLE and rheumatoid arthritis patients. Sera from patients with Raynaud's syndrome showed predominantly IgG reactivity with Fc gamma RIII. Sera from patients with progressive systemic sclerosis showed both IgG and IgM Fc gamma RII and Fc gamma RIII reactivity. Many patients diagnosed with degenerative osteoarthritis also had IgG autoantibodies, directed primarily against Fc gamma RII with lesser reactivity toward Fc gamma RIII. Further study is needed to correlate these findings to clinical characteristics of the different diseases.