Sixteen patients with osteoarthritis （13 knees and 3 hips）

3 patients with rheumatoid arthritis （RA） and 4 cadaver were studied for evidence of immune complex in the destroyed articular cartilage tissues. Frozen sections of the articular cartilage from arthroplasty were stained with fluoresceinated antibodies to human immunoglobulins IgG

IgA

IgM and complement C3. The results showed: 1. There were immune complexes linear deposited in the surface of the irregular articular cartilage tissues and on some chondro- cytes remained in most patients with osteoarthritis （14/16）. The patterns of immune complexes are IgA

complement C3

IgG and IgM

their percentage is 81. 25%

75%

75% and 50% respectively. 2. In all of 3 patients with RA

the surfaces of articular tissues were seen with patchy diffusely positive areas for IgA

IgG

IgM （excepting negative in I case） and complement C3. 3. There were no immune complexes deposited in the surfaces of 4 cases of normal articular tissues. The presence of immune complexes in the cartilages suggested that an autoimmune reaction participated in the pathological process of osteoarthritis and that the autoimmunity may be responsible for the continuous degeneration of the osteoarthritis.