Increase of CD57⁺ T cells in knee joints and adjacent bone marrow of rheumatoid arthritis (RA) patients: implication for an anti-inflammatory role

The distribution of CD57⁺ T and CD56⁺ T cells in patients with RA was examined. In control osteoarthritis patients, these cells exist as a minor population in the peripheral blood. Our data show that in patients with RA, CD57⁺ T cell levels are elevated in peripheral blood, knee joint fluid, knee synovial membrane and bone marrow (BM), compared with peripheral blood of controls. CD57⁺ T cells are especially high in knee joint fluid and joint-adjacent BM, while CD56⁺ T cells show no such increase. CD57⁺ T cells contain a major population of CD8⁺ cells and higher proportions of CD4⁻8⁻ cells and γδ T cells than do CD57⁻T cells. CD57⁺T cells in peripheral blood and joint fluid increase with the duration of disease. Erythrocyte sedimentation rate (ESR) is inversely correlated with the proportion of CD57⁺T cells in the joint fluid. Although RA frequently occurrs in patients with CD3⁺57⁺ cell leukaemia, and some CD57⁺T cells are likely to be involved in the onset of RA, we suggest that CD57⁺T cells may rather suppress inflammation of RA, and other cellular components (e. g. granulocytes) may govern the severity of the inflammation of RA. These CD57⁺ T cells are probably generated extrathymically in the adjacent BM or joint space.