Efficient T-cell priming and activation requires signaling through prostaglandin E2 (EP) receptors Sreeramkumar, Vinatha Hons, Miroslav ; https://orcid.org/0000-0002-6625-3348 Punzón, Carmen Stein, Jens Sancho, David Fresno Forcelledo, Manuel Cuesta, Natalia Understanding the regulation of T-cell responses during inflammation and auto-immunity is fundamental for designing efficient therapeutic strategies against immune diseases. In this regard, prostaglandin E 2 (PGE 2) is mostly considered a myeloid-derived immunosuppressive molecule. We describe for the first time that T cells secrete PGE 2 during T-cell receptor stimulation. In addition, we show that autocrine PGE 2 signaling through EP receptors is essential for optimal CD4 + T-cell activation in vitro and in vivo, and for T helper 1 (Th1) and regulatory T cell differentiation. PGE 2 was found to provide additive co-stimulatory signaling through AKT activation. Intravital multiphoton microscopy showed that triggering EP receptors in T cells is also essential for the stability of T cell-dendritic cell (DC) interactions and Th-cell accumulation in draining lymph nodes (LNs) during inflammation. We further demonstrated that blocking EP receptors in T cells during the initial phase of collagen-induced arthritis in mice resulted in a reduction of clinical arthritis. This could be attributable to defective T-cell activation, accompanied by a decline in activated and interferon-γ-producing CD4 + Th1 cells in draining LNs. In conclusion, we prove that T lymphocytes secret picomolar concentrations of PGE 2, which in turn provide additive co-stimulatory signaling, enabling T cells to attain a favorable activation threshold. PGE 2 signaling in T cells is also required for maintaining long and stable interactions with DCs within LNs. Blockade of EP receptors in vivo impairs T-cell activation and development of T cell-mediated inflammatory responses. This may have implications in various pathophysiological settings. Nature Publishing Group 2016 info:eu-repo/semantics/article doc-type:Article Article http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/1217 Sreeramkumar V, Hons M, Punzón C, et al. Efficient T-cell priming and activation requires signaling through prostaglandin E2 (EP) receptors. <i>Immunology and Cell Biology</i>. 2016;94(1):39-51. doi:<a href="https://doi.org/10.1038/icb.2015.62">10.1038/icb.2015.62</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1038/icb.2015.62 info:eu-repo/semantics/altIdentifier/wos/000367628600005 info:eu-repo/semantics/closedAccess