mPGES1-Dependent Prostaglandin E 2 (PGE 2 ) Controls Antigen-Specific Th17 and Th1 Responses by Regulating T Autocrine and Paracrine PGE 2 Production.

The integration of inflammatory signals is paramount in controlling the intensity and duration of immune responses. Eicosanoids, particularly PGE2 , are critical molecules in the initiation and resolution of inflammation and in the transition from innate to acquired immune responses. Microsomal PGE synthase 1 (mPGES1) is an integral membrane enzyme whose regulated expression controls PGE2 levels and is highly expressed at sites of inflammation. PGE2 is also associated with modulation of autoimmunity through altering the IL-23/IL-17 axis and regulatory T cell (Treg) development. During a type II collagen-CFA immunization response, lack of mPGES1 impaired the numbers of CD4+ regulatory (Treg) and Th17 cells in the draining lymph nodes. Ag-experienced mPGES1-/- CD4+ cells showed impaired IL-17A, IFN-γ, and IL-6 production when rechallenged ex vivo with their cognate Ag compared with their wild-type counterparts. Additionally, production of PGE2 by cocultured APCs synergized with that of Ag-experienced CD4+ T cells, with mPGES1 competence in the APC compartment enhancing CD4+ IL-17A and IFN-γ responses. However, in contrast with CD4+ cells that were Ag primed in vivo, exogenous PGE2 inhibited proliferation and skewed IL-17A to IFN-γ production under Th17 polarization of naive T cells in vitro. We conclude that mPGES1 is necessary in vivo to mount optimal Treg and Th17 responses during an Ag-driven primary immune response. Furthermore, we uncover a coordination of autocrine and paracrine mPGES1-driven PGE2 production that impacts effector T cell IL-17A and IFN-γ responses.