IL1F10 and rheumatoid arthritis: We examined the serum levels of IL-38 in RA patients, OA patients and healthy donors by using ELISA for human IL-38, and the corresponding levels were 5.7±0.94 ng/mL (n=137), 2.8±0.876 ng/mL (n=26), and 2.8±0.69 ng/mL (n=56), respectively.