TBX21 and rheumatoid arthritis: KLRD1, TBX21, and IL23R, the potential targets of piR-hsa-25672, piR-hsa-27620, and piR-hsa-23940, respectively, were all significantly downregulated, while the level of C4B, the potential target of piR-hsa-25672, was significantly higher in RA patients than that in HCs.