General mechanisms of inflammation in rheumatoid arthritis.

Rheumatoid synovitis is characterized by the simultaneous occurrence of two major types of immunologically-induced inflammation. These usually occur concurrently in the same joint. A cellular immune response is present in the sublining layer of the synovial membrane and an immune complex-induced acute inflammatory reaction is present in the synovial effusion phase of the disease. The two reactions are closely related and mutually interdependent. The cellular immune response is reduced in rheumatoid arthritis, but the chronic inflammatory cells of the synovium are active in the synthesis of IgG and probably considerable amounts of IgG rheumatoid factor. Rheumatoid factor complexes, particularly IgG-RF complexes, appear to be responsible for the exudative, immune complex-induced inflammatory phase of the disease.