TET2 Regulates CD8+ T Cell Responses to Acute and Chronic Viral Infection

Abstract DNA methylation is one of the major epigenetic mechanisms that controls cellular differentiation. The ten-eleven translocation (TET) family of methylcytosine dioxygenases mediates active DNA demethylation through the oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and subsequent intermediates. Here we demonstrate that TET2 regulates CD8+ T cell differentiation in vivo following acute and chronic viral infection. At steady-state, mice with a T-cell specific deletion of TET2 have intact thymic and peripheral T cell populations. Following acute viral infection with LCMV-Armstrong, TET2 loss enhances LCMV-specific CD8+ T cell memory differentiation in a cell-intrinsic manner without disrupting antigen-specific cell expansion or cytokine production. However, TET2-deficient memory CD8+ T cells exhibit altered recall responses with blunted re-expansion, retained expression of phenotypic memory markers and restricted re-expression of activation markers. During chronic viral infection with LCMV-clone 13, TET2 controls CD8+ T cell expansion and alters differentiation. Importantly, though mice with T-cell specific loss of TET2 developed similar levels of CD8+ T cell exhaustion as wild-type mice, TET2 loss specifically reduced PD-1 expression suggesting that TET2 may direct DNA demethylation of the PD-1 locus. Together, our data indicate that TET2 is an important regulator of CD8+ T cells following both acute and chronic viral infections and suggest targeting epigenetic regulators have potential for enhancing antiviral immunity. Disclosures No relevant conflicts of interest to declare

mTORC2 regulates multiple aspects of NKT‐cell development and function

Invariant NKT (iNKT) cells bridge innate and adaptive immunity by rapidly secreting cytokines and lysing targets following TCR recognition of lipid antigens. Based on their ability to secrete IFN-γ, IL-4 and IL-17A, iNKT-cells are classified as NKT-1, NKT-2, and NKT-17 subsets, respectively. The molecular pathways regulating iNKT-cell fate are not fully defined. Recent studies implicate Rictor, a required component of mTORC2, in the development of select iNKT-cell subsets, however these reports are conflicting. To resolve these questions, we used Rictorfl/fl CD4cre+ mice and found that Rictor is required for NKT-17 cell development and normal iNKT-cell cytolytic function. Conversely, Rictor is not absolutely required for IL-4 and IFN-γ production as peripheral iNKT-cells make copious amounts of these cytokines. Overall iNKT-cell numbers are dramatically reduced in the absence of Rictor. We provide data indicating Rictor regulates cell survival as well as proliferation of developing and mature iNKT-cells. Thus, mTORC2 regulates multiple aspects of iNKT-cell development and function

The Methylcytosine Dioxygenase TET2 Regulates CD8+ T Cell Memory Differentiation

Abstract DNA methylation is one of the major epigenetic mechanisms that control T cell differentiation. The ten-eleven translocation (TET) family of methylcytosine dioxygenases converts 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and other oxidized methylcytosines, intermediates in active DNA demethylation. Here we demonstrate that TET2 regulates CD8+ T cell differentiation in vivo following acute viral infection. At steady-state, mice with a T-cell specific deletion of TET2 have intact thymic and peripheral T cell populations. However, following acute viral infection with LCMV-Armstrong, TET2 loss promotes early acquisition of a memory CD8+ T cell fate in a cell-intrinsic manner without disrupting antigen-driven cell expansion or effector function. Integration of genome-wide methylation analysis and expression data suggest that TET2 loss leads to hypermethyation of the PRDM1 genomic locus (encoding Blimp-1) and alters the relative expression of Blimp-1 and Bcl-6, two antagonistic transcriptional repressors known to direct CD8+ T cell memory differentiation. Together, our data indicate that TET2 is an important regulator of CD8+ T cell fate decisions. Disclosures No relevant conflicts of interest to declare

The Loss of TET2 Promotes CD8(+) T Cell Memory Differentiation

T cell differentiation requires appropriate regulation of DNA methylation. In this article, we demonstrate that the methylcytosine dioxygenase ten-eleven translocation (TET)(2) regulates CD8(+) T cell differentiation. In a murine model of acute viral infection, TET2 loss promotes early acquisition of a memory CD8(+) T cell fate in a cell-intrinsic manner without disrupting Ag-driven cell expansion or effector function. Upon secondary recall, TET2-deficientmemory CD8(+) T cells demonstrate superior pathogen control. Genome-wide methylation analysis identified a number of differentially methylated regions in TET2-deficient versus wildtype CD8(+) T cells. These differentially methylated regions did not occur at the loci of differentially expressed memory markers; rather, several hypermethylated regions were identified in known transcriptional regulators of CD8(+) T cell memory fate. Together, these data demonstrate that TET2 is an important regulator of CD8(+) T cell fate decisions

T-cell receptor signals direct the composition and function of the memory CD8+ T-cell pool

SH2 domain-containing leukocyte phosphoprotein of 76 kDa (SLP-76) nucleates a signaling complex critical for T-cell receptor (TCR) signal propagation. Mutations in the tyrosines of SLP-76 result in graded defects in TCR-induced signals depending on the tyrosine(s) affected. Here we use 2 strains of genomic knock-in mice expressing tyrosine to phenylalanine mutations to examine the role of TCR signals in the differentiation of effector and memory CD8+ T cells in response to infection in vivo. Our data support a model in which altered TCR signals can determine the rate of memory versus effector cell differentiation independent of initial T-cell expansion. Furthermore, we show that TCR signals sufficient to promote CD8+ T-cell differentiation are different from those required to elicit inflammatory cytokine production