Decreased serum IL-35 and IL-37 in COPD patients with severe emphysema

Abstract Background Chronic obstructive pulmonary disease(COPD) is a heterogeneous syndrome and chronic persistent inflammation has been discovered to play critical role in the structural damage leading to the progression of emphysema. IL-35 and IL-37 are both immune-suppressing cytokines which exert inhibitory effects on a lot of inflammatory disorders. This study aimed to determine the correlation between serum levels of IL-35 and IL-37 with the severity of emphysema and clinical parameters of COPD patients. Methods We detected the serum levels of IL-35, IL-37 and IL-33 from 64 Chinese patients with stable COPD by using an enzyme-linked immunosorbent assay and examined the association of their concentrations with COPD patients’ clinical parameters. Results The serum levels of IL-35 and IL-37 were significantly decreased in the COPD patients with severe emphysema subtype compared to non-emphysema or mild-to-moderate emphysema subtype. The serum level of IL-35 was correlated with body mass index(BMI), modified Medical Research Council(mMRC) score and the concentrations of IL-33 and IL-37. The lower IL-35 group exhibited decreased BMI, lower FEV₁/FVC, severe extent of emphysema and worse mMRC. Multivariable regression showed that lower FEV₁/FVC, worse mMRC score and decreased serum levels of IL-35 were independently associated with severe emphysema. Conclusions We found that the serum IL-35 and IL-37 levels were decreased in severe emphysema subtype. The lower level of IL-35 was correlated with lower BMI and worse mMRC score. IL-35 concentrations, FEV1/FVC and mMRC score were independently associated with the extent of emphysema.