CD28 and Arthritis: Furthermore, among the four T-cell subsets transferred to CIA mice, CD4+CD28−OX40+ T cells displayed the most significant pathogenic role in arthritis development compared with CD4+CD28−OX40− (P = 0.011), CD4+CD28+OX40− (P < 0.001), and CD4+CD28+OX40+ (P < 0.001) T cells.