Decreased expression of interleukin‑37 and its anti‑inflammatory effect in allergic rhinitis.

Interleukin‑37 (IL‑37), a novel member of the IL‑1 cytokine family has been identified as a natural suppressor of innate immunity and inflammatory responses. The present study aimed to determine the expression of IL‑37 in peripheral blood mononuclear cells (PBMCs) from patients with allergic rhinitis (AR), and examine the possible immunosuppressive effect of IL‑37 on inflammatory mediators and CD4+ T cells in the pathogenesis of AR. The expression levels of IL‑37 were determined in PBMCs from 39 patients with AR and 43 controls using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) analysis and flow cytometry. Cytokines in the supernatants of the PBMCs and CD4+ T cells, which were stimulated with lipopolysaccharide in the presence or absence of IL‑37, were assayed using enzyme‑linked immunosorbent assays and RT‑qPCR analysis. The results showed that the patients with AR exhibited significantly decreased expression of IL‑37, and increased expression levels of interleukin (IL)‑1β and IL‑6 in PBMCs. Recombinant IL‑37 (rIL‑37) inhibited the production of IL‑1p and IL‑6, and enhanced the production of IL‑27 in PBMCs from the patients with AR and the control individuals. rIL‑37 also markedly decreased the expression of IL‑17 by CD4+ T cells in the patients with AR and controls. These results suggested that IL‑37 may be an important cytokine in the pathogenesis of AR. It may have a protective role in AR by inhibiting the production of proinflammatory cytokines and through suppressive regulation of the Th17 response.