Combined use of etanercept and MTX restores CD4+/CD8+ ratio and Tregs in spleen and thymus in collagen-induced arthritis

To further explore the mechanism of etanercept (ENT, rhTNFR:Fc) and methotrexate (MTX) in the combined treatment of rheumatoid arthritis (RA), we investigated whether thymic and splenic T-cell subsets and their related cytokines imbalance could be restored by ETN/MTX treatment. The effect of ETN/MTX on collagen-induced arthritis (CIA) was evaluated by arthritis scores, joint and spleen histopathology, as well as indices of thymus and spleen. T lymphocytes proliferation was determined by [H-3]-TdR incorporation. Levels of TNF-alpha, LT-alpha, IL-1 beta, RANKL, IL-10, IL-17, IFN-gamma and IL-6 were detected by enzyme linked immunosorbent assay. The subsets of T lymphocytes including CD4(+), CD8(+), CD3(+)CD4(+), CD4(+)CD25(+), CD4(+)CD62L(+) and CD4(+)CD25(+)Foxp3(+) cells were quantified using flow cytometry. Combined administration of ETN/MTX significantly inhibited the proliferation of T lymphocytes, decreased serum IL-6, TNF-alpha, IL-1 beta, RANKL and macrophage supernatant IL-17, LT-alpha, increased serum IFN-gamma and macrophage supernatant IL-10. Moreover, the combined administration could restore CD4(+)/CD8(+) ratio and Treg cells of CIA thymus and spleen. Taken together, our findings suggest that ENT/MTX may modify the abnormal T lymphocytes balance from central to peripheral lymphoid organs, which may partially, explained the mechanism of the combined administration.