HLA-DR Antigen Positive Cells in the RA Synovium. -Their Significant Role Concerning in the Continuation of Chronic Inflammation of RA.

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1 Characteristics of RA synovial cells The sublining D cells which were remarkably proliferating in the rheumatoid synovial membrane were divided into two type cells, D(F) cells and D(M) cells immunohistochemically. In culture, D(F) cells showed high proliferative activity and easily transformed their morphological and functional character under the effects of variable cytokines. On the other hand, D(M) cells proliferated very slowly, and they contiguously and strongly expressed HLA-DR antigen on their surface. These findings suggest that D(F) cell plays an important role in formation of histopathological variety of RA synovitis and D(M) cell is largely concerned in the immunological activity of RA. 2 Histopathological study of early stage of synovial lesion We investigated the early stage of RA synovitis immunohistochemically and from this study it become clear that in very early of RA, HLA-DR positive cells were found in pericapillary region and following them T lymphocytes appeared and B lymphocytes appeared to aggregate in later. 3 The effects of drugs on RA synovitis Some patients with early stage RA showed improvement of condition of disease after treatment with immunomodulating drug (CCA), but no apparent qualitative and quantitative changes of HLA-DR positive cells in synovium were observed. These findings suggest the complexity of cellular interaction in development of RA synovitis. 4 Comparison of synovial cells with cells in rheumatoid nodule The characteristics of majority of cells in rheumatoid nodule were quite similar to that of D cells in rheumatoid synovitis. Clinically rheumatoid synovitis is characterized by its progressive and destructive nature in contrast to rheumatoid nodule. Histopathologically in the rheumatoid nodule the lymphocyte infiltration was less conspicuous. These findings suggest that lymphocyte infiltration is essential for the continuation of chronic destructive inflammation of RA synovitis.