Moreover, the synovial membrane level of TNF-α mRNA expression, one of the key effector cytokines in Tc1 cells, in AOSD was significantly increased compared with osteoarthritis but remained significantly lower than that observed in rheumatoid arthritis [24], allowing us to assume that some relevant cells may produce this cytokine in developing arthritis during AOSD. Here, TNF is linked to arthritic joint disease.