[Immunopathological study of synovium of rheumatoid arthritis]

46 patients with different rheumatic disorders were subjected to arthroscopic examination and the biopsied synovia were studied immunopathologically. Immunoglobulins, complements and fibrinogen deposition were detected by direct immunofluorescence, and rheumatoid factor (RF) deposition was detected by peroxidase-labelled denatured human IgG. Postoperative diagnosis of these cases were as follows: rheumatoid arthritis (RA) 21; seronegative spondylarthropathy 4; reactive arthritis 2; unidentified synovitis 4; osteoarthritis 8; and nonsynovitis conditions 5. It was shown that the positive rates of deposition of IgG, IgM, complement C3, C1q and C4, and RF in RA were 95.2%, 52.4%, 38.1%, 28.6%, 9.5% and 42.9%, respectively. Deposition was negative in all other rheumatic diseases. The positive fibrinogen deposition rate in RA was 42.9%; it was weakly positive in other disorders as well. The results indicate that the pathogenesis of RA is related to humoral immunity, and immunopathological study of the synovium has very important diagnostic significance in RA. On the other hand, deposition of fibrinogen lacks specificity for any rheumatic disease. The deposition of RF IgG, IgM and complement C3, C1q and C4 in the synovium of RA patients does not correlate well with clinical disease activity. The deposition of RF in the synovium also does not show paired correlation with blood IgM RF determination. This difference may be explained by the fact that the synovial RF examined in the present study may include all isotypes of RF and that hidden-RF in the blood may give a negative result. The synovium is the site of production of RF, but the degree of pathological change of the synovium of different joints in a single patient may not be uniform. The results of humoral immunity studies of the RA synovium may be influenced by the site selected for synovial biopsy.