Upregulation of PD-L1 Expression by Prostaglandin E and the Enhancement of IFN-γ by Anti-PD-L1 Antibody Combined With a COX-2 Inhibitor in Infection.

Bovine mycoplasmosis caused by results in pneumonia and mastitis in cattle. We previously demonstrated that the programmed death 1 (PD-1)/PD-ligand 1 (PD-L1) pathway is involved in immune dysfunction during infection and that prostaglandin E (PGE) suppressed immune responses and upregulated PD-L1 expression in Johne's disease, a bacterial infection in cattle. In this study, we investigated the role of PGE in immune dysfunction and the relationship between PGE and the PD-1/PD-L1 pathway in infection. stimulation with upregulated the expressions of PGE and PD-L1 presumably via Toll-like receptor 2 in bovine peripheral blood mononuclear cells (PBMCs). PGE levels of peripheral blood in infected cattle were significantly increased compared with those in uninfected cattle. Remarkably, plasma PGE levels were positively correlated with the proportions of PD-L1 monocytes in -infected cattle. Additionally, plasma PGE production in infected cattle was negatively correlated with -specific interferon (IFN)-γ production from PBMCs. These results suggest that PGE could be one of the inducers of PD-L1 expression and could be involved in immunosuppression during infection. blockade assays using anti-bovine PD-L1 antibody and a cyclooxygenase 2 inhibitor significantly upregulated the -specific IFN-γ response. Our study findings might contribute to the development of novel therapeutic strategies for bovine mycoplasmosis that target PGE and the PD-1/PD-L1 pathway.