Among SLE patients, a significant positive correlation was observed between the percentage of OX40 expression on CD4+ T-cells and serum creatinine levels (r=0.78, P<.01) (Figure 1), and between OX40 expression and disease activity measured by SLEDAI (r=0.66, P<.01) (Figure 2). Here, CD4 is linked to systemic lupus erythematosus.