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T cell‐mediated antitumor immunity is modulated, in part, by N‐glycosylation. However, the interplay between N‐glycosylation and the loss of effector function in exhausted T cells has not yet been fully investigated. Here, we delineated the impact of N‐glycosylation on the exhaustion of tumor‐infiltrating lymphocytes in a murine colon adenocarcinoma model, focusing on the IFN‐γ‐mediated immune response. We found that exhausted CD8+ T cells downregulated the oligosaccharyltransferase complex, which is indispensable for N‐glycan transfer. Concordant N‐glycosylation deficiency in tumor‐infiltrating lymphocytes leads to loss of antitumor immunity. Complementing the oligosaccharyltransferase complex restored IFN‐γ production and alleviated CD8+ T cell exhaustion, resulting in reduced tumor growth. Thus, aberrant glycosylation induced in the tumor microenvironment incapacitates effector CD8+ T cells. Our findings provide insights into CD8+ T cell exhaustion by incorporating N‐glycosylation to understand the characteristic loss of IFN‐γ, opening new opportunities to amend the glycosylation status in cancer immunotherapies. [ABSTRACT FROM AUTHOR]

Allergic responses are characterized by the activation of a specific subset of effector CD4+ T cells, the T‐helper type 2 (Th2) cells, that respond to harmless environmental antigens causing inflammation and pathology. Th2 cells are also found in the context of parasite infections, where they can mediate parasite clearance and expulsion, and support tissue repair. The process that leads to the activation of Th2 cells in vivo is incompletely understood: while it has become clear that "conventional" dendritic cells are essential antigen‐presenting cells for the initiation of Th2 immune responses, the molecules that are expressed by dendritic cells exposed to allergens, and the mediators that are produced as a consequence and signal to naïve CD4+ T cells to promote their development into effector Th2, remain to be defined. Here we summarize recent developments in the identification of the dendritic cell subsets involved in Th2 responses, review potential mechanisms proposed to explain the generation of these immune responses, and discuss the direct and indirect signals that condition dendritic cells to drive the development of Th2 responses during allergen or parasite exposure. [ABSTRACT FROM AUTHOR]

Diacylglycerol kinase (DGK)-mediated consumption of the diacylglycerol (DAG) generated in response to antigen recognition is an important mechanism to limit T-cell function. Targeting DGK activity presents new opportunities for therapeutic manipulation of the immune response, but assessment of individual DGK functions is complex. T cells express two DGK isoforms, DGKα and DGKζ, and there are no isoform-specific inhibitors. Here we used short interfering RNA-mediated gene silencing in human T cells and DGKα- and DGKζ-deficient mice to define DGK isoform-specific regulation of key signaling pathways during T-cell activation. Our results identify DGKζ as the predominant brake on basal/tonic conditions as well as on downstream T-cell receptor/co-stimulatory signals. DGKζ silencing triggers basal RasGTP activation and facilitates enhanced membrane stability of protein kinase C alpha as well as increased activity of AGC kinases. Downstream of T-cell receptor/co-stimulation, DGKζ silencing results in enhanced and maintained recruitment of PKC theta to the membrane, as well as phosphoinositide-dependent protein kinase-1 activation and scaffolding functions. Our studies identify a previously unrecognized DGKζ contribution as a negative regulator of the crosstalk between phospholipase C-gamma- and phosphoinositide 3-kinase-regulated pathways. This DGKζ input helps to explain previous observations in DGK-deficient mice and suggests that the development of isoform-specific DGK inhibitors is of great interest for the manipulation of distinct aspects of T-cell responses. [ABSTRACT FROM AUTHOR]

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 E2 (PGE2) is mostly considered a myeloid-derived immunosuppressive molecule. We describe for the first time that T cells secrete PGE2 during T-cell receptor stimulation. In addition, we show that autocrine PGE2 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. PGE2 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 PGE2, which in turn provide additive co-stimulatory signaling, enabling T cells to attain a favorable activation threshold. PGE2 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. [ABSTRACT FROM AUTHOR]