HTLV-1 infection and synovitis: Histopathological analysis of the synovial tissue.

Histopathological analysis of the synovial tissues from 7 cases of HTLV-1 carriers who had chronic arthritis was performed. Synovial tissues showed villous proliferation to a various degree. Proliferation of synovial stromal cells associated with interstitial edema and proliferation of small blood vessels was observed. Lymphocytic infiltration was rather diffuse without evident lymph-follicle like structures. The most characteristic feature was the presence of atypical lymphocytes with nuclear convolution in the synovial tissues. Immunohistochemical analysis of the synovial tissues revealed infiltration both of CD4 and CD8 positive lymphocytes, accompanied with the expression of HLA-DR antigens on the synovial cells.These findings suggest that HTLV-1 infection might play an important role in the pathogenesis of the arthritis. Further examination of the function of HTLV-1 infected cells in the arthropathy is necessary.