ANTIBODIES TO SYNOVIAL ANTIGENS IN RECENT-ONSET RHEUMATOID-ARTHRITIS

Objective, To identify synovial antigens that bind to serum antibodies from subjects with recent-onset rheumatoid arthritis (RA) (<6 months of synovitis), Methods. Soluble and insoluble fractions of Triton X-100 extracts of RA and normal synovial tissue, and normal spleen and placenta, were immunoblotted with sera from 27 patients with recent-onset RA, 13 autoimmune disease control subjects, and 13 blood bank control donors, Bound immunoglobulin was probed with I-125-labeled protein A, Results, Antibodies in the sera of 20 (74%) patients with recent-onset RA recognized at least 1 of 5 antigens in both a disease- and tissue-specific and nonspecific manner, Anti-La antibodies, usually associated with primary Sjogren's syndrome, were detected in 2 sera, Eight sera had increased reactivity to an IgG heavy and light chain dimer, There was strong binding of 8 sera with a 35-kd doublet and of 3 sera with a 55-kd species in RA and normal synovial lysates (insoluble fractions), Two sera uniquely recognized a 45-kd protein only in the RA synovial lysate (soluble fraction), Conclusion. IgG antibodies in the sera of patients with recent-onset RA show positive immunoblots for 3 novel synovial antigens of 35-kd, 55-kd, and 45-kd, as well as for 2 previously characterized antigens (La and IgG), Thus, a variety of synovial antigens appear to be recognized by B cells even early in the clinical course of RA.