IL-37b suppresses T cell priming by modulating dendritic cell maturation and cytokine production via dampening ERK/NF-κB/S6K signalings.

Interleukin 37b (IL-37b) plays a key role in suppressing immune responses, partially by modulating the function of dendritic cells (DCs). However, the precise mechanisms are still largely unknown. Here, we investigated the effects of IL-37b on DC maturation and T cell responses induced by DCs, and explored the involved signaling pathways. It was found that IL-37b down-regulated the expressions of co-stimulatory molecules CD80 and CD86 on DCs in vitro. At the same time, the expressions of pro-inflammatory cytokines, such as TNF-α and IL-6, were suppressed, while the expression of the T cell inhibitory cytokine TGF-β was increased in IL-37b-treated DCs. In addition, the activation effect of DCs on T cells was impaired by IL-37b. We further revealed that extracellular single-regulated kinase (ERK), nuclear factor-κB (NF-κB), and mTOR-S6K signaling pathways were involved in the inhibition of DCs induced by IL-37b. This was confirmed by the similarly suppressive effect of chemical inhibitors against NF-κB, ERK, and S6K on the expressions of IL-6 and TNF-α in DCs. In conclusion, these results demonstrated that IL-37b suppressed DC maturation and immunostimulatory capacity in T cell priming by involving in ERK, NF-κB, and S6K-based inhibitory signaling pathways.