An immunohistological analysis of lymphocyte subpopulations and their microenvironment in the synovial membranes of patients with rheumatoid arthritis using monoclonal antibodies.

We have used monoclonal antibodies of the orthoclone (OKT) series to identify T cell subsets in an immunohistological analysis of the synovial membranes obtained from normal individuals and patients with osteoarthritis or rheumatoid arthritis. T cells of the inducer and the suppressor/cytotoxic subsets were identified by the OKT4 and OKT8 antibodies respectively while HLA-DR (Ia-like) antigens were recognized by a conventional antiserum. In the normal and osteoarthritic synovial membranes, virtually no lymphocytes were identified whereas the mononuclear cell infiltrates of the rheumatoid synovial membranes were composed predominantly of T cells expressing the OKT4 inducer phenotype with few OKT8+ suppressor/cytotoxic cells. The OKT4+ cells were found to be intimately related to B cells and strongly HLA-DR+ cells which morphologically resembled the interdigitating cells of lymph nodes. The micro-anatomical arrangement of these different cell types in the mononuclear infiltrates of the rheumatoid synovial membranes closely resembled that of the paracortical or T cell dependent area of normal lymph nodes except few OKT8+ lymphocytes were present. These findings are explained in terms of rheumatoid arthritis as a disease of altered T lymphocyte/macrophage immunoregulation.