CD40LG and rheumatoid arthritis: Rheumatoid arthritis (RA) as an autoimmune disease is characterized by the presence in the blood serum and synovial fluid of a wide range of autoantibodies with different specificity, including rheumatoid factors (RFs) of classes IgM, IgA, and IgG, as well as autoantibodies, reacting with various antigenic epitopes.