T-lymphocyte subsets and HLA-DR-expressing cells in the osteoarthritic synovialis.

Rheumatoid and osteoarthritic synovial membranes biopsied at operations were analysed in frozen sections with an immunohistochemical monoclonal antibody technique. It is evident from this investigation that immunocompetent inflammatory cells such as HLA-DR-expressing non-T cells and T cells in general occur even in the osteoarthritic synovial membrane, though to a lesser degree than in rheumatoid arthritis. In about half of the osteoarthritic synovial membranes these T cells were clustered in follicle-like formations. In both diseases, most of the T cells were helper/inducer T cells whereas cytotoxic/suppressor T cells occur sparsely and almost exclusively in rheumatoid arthritis.