TNFSF18 and systemic lupus erythematosus: As shown in Figure 2, serum GITRL levels in SLE patients with active disease were significantly higher than those with inactive disease (403.3 ± 81.23 ng/mL versus 136.3 ± 34.41 ng/mL; P = 0.0043), furthermore serum GITRL levels were positively correlated with SLEDAI (r = 0.317; P = 0.018), indicating a close correlation of increased GITRL expression with SLE disease activity.