Serum IL-23 concentrations were higher in COPD patients of GOLD 3–4 (689.05 ± 107.16 ng/L), mMRC score of 4 (701.38 ± 97.29 ng/L) and longer clinical medical history (724.76 ± 120.12 ng/L) than in those of GOLD 1–2 (586.78 ± 116.56 ng/L) (t = − 4.832, p < 0.001) (Supp. The gene discussed is IL37; the disease is chronic obstructive pulmonary disease.