Specificity and class distribution of FcγR-specific autoantibodies in patients with autoimmune disease

To investigate the prevalence of autoantibodies directed against FcγRII (CD32) and FcγRIII (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 FcγRII and FcγRIII protein. Class specificity was defined with anti-IgG, anti-IgM, and anti-IgA reagents. High titers of circulating IgM autoantibodies reacting with both FcγRII and FcγRIII were characteristic for SLE and rheumatoid arthritis patients. Sera from patients with Raynaud's syndrome showed predominantly IgG reactivity with FcγRIII. Sera from patients with progressive systemic sclerosis showed both IgG and IgM FcγRII and FcγRIII reactivity. Many patients diagnosed with degenerative osteoarthritis also had IgG autoantibodies, directed primarily against FcγRII with lesser reactivity toward FcγRIII. Further study is needed to correlate these findings to clinical characteristics of the different diseases.