Up-regulation of EP and EP receptors in human tolerogenic dendritic cells boosts the immunosuppressive activity of PGE

Dendritic cells (DCs) are APCs essential in regulating the immune response. PGE, produced during inflammation, has a pivotal role in the maturation of DCs and, therefore, is vital for the immune response. The large variety of biologic functions governed by PGE is mediated by its signaling through 4 distinct E-type prostanoid (EP) receptors. Immunogenic DCs express EP and EP, which mediate the PGE signaling. However, the expression and function of EP receptors in human tolerogenic DCs (tol-DCs), which present an inhibitory phenotype, have not yet, to our knowledge, been assessed. To clarify the role of EP receptors in tol-DCs, we examined the expression of different EP receptors and their effect using selective agonists in human cells. We find that EP and EP expression are up-regulated in in vitro–generated tol-DCs compared with mature DCs (mDCs). Activation of EP –EP has a direct effect on the surface expression of costimulatory molecules and maturation receptors, such as CD80, CD83, and CD86 or MHCII and CCR7 in tol-DCs, the latter being exclusively modulated by PGE –EP signaling. Importantly, we find that EP and EP receptors are involved in tolerance induction through IL-10 production by tol-DCs. These results are in sharp contrast with the inflammatory role of EP. Moreover, we show that DCs generated in the presence of agonists for EP receptors, induce naive T cell differentiation toward polarized Th1/Th17 cells. Given the differential effects of EP receptors, our results suggest that EP receptor agonist/antagonists might become relevant novel drug templates to modulate immune response.