Histopathology of Rheumatoid Arthritis

Abstract

  Synovitis of rheumatoid arthritis（RA）starts as the infiltration of CD3 T-cells around the capillaries in sublining connective tissues. An RA-specific histopathologic finding may be the polymorphous proliferation of fibroblasts in sublining layer, probably due to proinflammatory cytokines such as IL-1 and TNFa. The amount of infiltrating inflammatory cells in synovitis lesions does not correlate to the bone destruction of affected joints. Pannus destroys the bone, and the infiltration of lymphocytes and plasma cells in proliferating synovial tissue does not reflect the extent of pannus formation. Treatment of RA with biologic agents causes the thinning of synovial layer, the decrease of inflammatory cell infiltration, and the fibrosis of synovial tissue. The remarkable effects of biologic agents on RA synovitis lesion indicate the importance of targeted cytokines in the pathogenesis of RA synovitis. Therefore, it is important to take notice of the histopathologic findings reflecting the biologic effects of these cytokines.