We analyzed the relationship between IL-37 and disease activity in RA patients, and found that plasma IL-37 was positively correlated with CRP (Fig. 4A, R = 0.4738, P = 0.0005) and the DAS28 score (Fig. 4B, R = 0.5454, P<0.0001) in RA patients. Here, CRP is linked to rheumatoid arthritis.