IL-37 is a cytokine of the interleukin 1 (IL-1) family with potent anti-inflammatory effects on innate immunity. In the Proceedings of the National Academy Sciences, Fujita and colleagues use a contact hypersensitivity model with the hapten DNFB to demonstrate that IL-37 is also able to dampen adaptive immunity. Although functional IL-37 is not expressed by mice, human IL-37 expressed trangenically is effective. Mice with trangenic expression of human IL-37 do not express the protein constitutively but upregulate expression locally in the skin after application of DNFB, and such mice prove resistant to the subsequent induction of contact hypersensitivity. The number, migration and phagocytosis of dendritic cells (DCs) in the skin of these mice are all normal; however, bone marrow–derived DCs from these mice have poor antigen-presenting ability. The impaired function of these DCs is probably due to their lower expression of major histocompatibility complex class II and the costimulatory receptor CD40 and production of inflammatory cytokines, as well as an increase in anti-inflammatory IL-10.

Proc. Natl. Acad. Sci. USA (7 October 2014) doi:10.1073/pnas.1416714111