TNFRSF9 and systemic lupus erythematosus: In SLE patients, %CD4+CD137+ cells positively correlated with SLEDAI-2K (p = 0.0082, r = 0.58, CI (0.15–0.82); indeed, %CD4+CD137+ cells were significantly lower in SLE patients with a remission status compared to those not reaching this condition (median 1.07 (IQR 0.91) versus 1.58 (IQR 2.42), p = 0.013).