PRF1 and rheumatoid arthritis: GO enrichment analysis detected several GO terms such as T cell–mediated cytotoxicity, positive regulation of T cell–mediated cytotoxicity, lymphocyte mediated immune regulation, cell killing regulation, Th17 cell differentiation, antigen processing and presentation via MHC class I for endogenous peptide antigens, antigen processing and presentation via MHC class Ib, autoimmune thyroid disease, etc. Some researchers have detected cd4t cells with cytotoxic potential in RA and AS and are able to mediate graft rejection through a perforin-dependent mechanism (43).