CD28 and rheumatoid arthritis: Importantly, we found 13 core region genes, including IL2RB, STAT4, TYK2, BLK, TNFAIP3, EOMES, IL6R, IRAK1, TRAF6, CD28, TRAF1, PTPRC, and IL2RA. These core region genes could be used as potential therapeutic sites for the treatment of RA.