TNFRSF4 and rheumatoid arthritis: To gain further insight into the observed correlation between OX40L expression by SMs and DAS28 scores, the three CD4+ T cell subsets most closely related to OX40/OX40L signaling (Tfh, Th1, and Tregs) were examined, given that they can control RA-related inflammatory activity and immune responses [6,8,19,29].