TIGIT negatively regulates inflammation by altering macrophage phenotype.

Macrophages function as an essential component of innate immune system, contributing to both the initiation and appropriate resolution of inflammation. The exposure of macrophages to the microbial products, such as lipopolysaccharide (LPS), can strongly shift the balance between tissue homeostasis and inflammation in favor of causing systemic damage, in which macrophage M1 polarization play important roles. Strategies aiming at restoring the balance of macrophage polarization remain to be further explored. Herein, we have demonstrated that poliovirus receptor (PVR), the receptor of TIGIT, was dramatically upregulated on the surface of mouse peritoneal macrophages when exposed to LPS. TIGIT-Fc fusion protein not only inhibited the macrophage activation, but also skewed M1/M2 balance toward an anti-inflammatory profile, especially enhanced the secretion of IL-10. The activation of TIGIT/PVR pathway in macrophages correlated with increased nuclear translocation of c-Maf, which promotes IL-10 transcription. Treatment with fibroblasts stably secreting TIGIT-Fc fusion protein significantly reversed the lethal and sublethal endotoxic shock, which facilitated peritoneal macrophages to switch towards anti-inflammatory M2 cytokine profiles. These findings highlight a novel role of the TIGIT/PVR pathway in macrophage M2 polarization and suggest that TIGIT may have the potential to optimize the treatment of macrophage-involved inflammatory diseases.