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The pancreatic islet microenvironment is highly oxidative, rendering β cells vulnerable to autoinflammatory insults. Here, we examined the role of islet resident macrophages in the autoimmune attack that initiates type 1 diabetes. Islet macrophages highly expressed CXCL16, a chemokine and scavenger receptor for oxidized low-density lipoproteins (OxLDLs), regardless of autoimmune predisposition. Deletion of Cxcl16 in nonobese diabetic (NOD) mice suppressed the development of autoimmune diabetes. Mechanistically, Cxcl16 deficiency impaired clearance of OxLDL by islet macrophages, leading to OxLDL accumulation in pancreatic islets and a substantial reduction in intra-islet transitory (Texint) CD8+ T cells displaying proliferative and effector signatures. Texint cells were vulnerable to oxidative stress and diminished by ferroptosis; PD-1 blockade rescued this population and reversed diabetes resistance in NOD. Cxcl16 −/− mice. Thus, OxLDL scavenging in pancreatic islets inadvertently promotes differentiation of pathogenic CD8+ T cells, presenting a paradigm wherein tissue homeostasis processes can facilitate autoimmune pathogenesis in predisposed individuals. [Display omitted] • CXCL16 in islet resident macrophages is crucial for OxLDL clearance in islets • Cxcl16 deletion in NOD mice suppresses T1D via an islet-specific mechanism • OxLDL exposure diminishes intra-islet transitory CD8+ T cells through ferroptosis • PD-1 blockade rescues transitory CD8+ T cells and reverses diabetes resistance Pancreatic islet β cells are highly sensitive to autoinflammatory insults, in part due to their highly oxidative microenvironment. Srivastava et al. report that CXCL16 on resident islet macrophages scavenges OxLDL in pancreatic islets. This process, which supports tissue homeostasis, inadvertently promotes the differentiation of pathogenic CD8+ T cells and autoimmune diabetes, underscoring a pathogenic role of the tissue microenvironment in autoimmunity. [ABSTRACT FROM AUTHOR]

CD8 + T cell exhaustion (T EX ) impairs the ability of T cells to clear chronic infection or cancer. While T EX are hypofunctional, some T EX retain effector gene signatures, a feature associated with killer lectin-like receptor (KLR) expression. Although KLR + T EX (T KLR ) may improve control of chronic antigen, the signaling molecules regulating this population are poorly understood. Using single-cell RNA sequencing (scRNA-seq), flow cytometry, RNA velocity, and single-cell T cell receptor sequencing (scTCR-seq), we demonstrate that deleting the pseudokinase Trib1 shifts T EX toward CX3CR1 + intermediates with robust enrichment of T KLR via clonal T cell expansion. Adoptive transfer studies demonstrate this shift toward CD8 + T KLR in Trib1-deficient cells is CD8 intrinsic, while CD4-depletion studies demonstrate CD4 + T cells are required for improved viral control in Trib1 conditional knockout mice. Further, Trib1 loss augments anti-programmed death-ligand 1 (PD-L1) blockade to improve viral clearance. These data identify Trib1 as an important regulator of CD8 + T EX whose targeting enhances the T KLR effector state and improves checkpoint inhibitor therapy., Competing Interests: Declaration of interests E.J.W. is a member of PICI and advisor for Danger Bio, Marengo, Janssen, New Limit, Pluto Immunotherapeutics, Related Sciences, Rubius Therapeutics, Synthekine, and Surface Oncology. E.J.W. is a founder of Surface Oncology, Danger Bio, and Arsenal Biosciences., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Reinvigoration of exhausted CD8+ T (Tex) cells by checkpoint immunotherapy depends on the activation of precursors of exhausted T (Tpex) cells, but the local anatomical context of their maintenance, differentiation, and interplay with other cells is not well understood. Here, we identified transcriptionally distinct Tpex subpopulations, mapped their differentiation trajectories via transitory cellular states toward Tex cells, and localized these cell states to specific splenic niches. Conventional dendritic cells (cDCs) were critical for successful αPD-L1 therapy and were required to mediate viral control. cDC1s were dispensable for Tpex cell expansion but provided an essential niche to promote Tpex cell maintenance, preventing their overactivation and T-cell-mediated immunopathology. Mechanistically, cDC1s insulated Tpex cells via MHC-I-dependent interactions to prevent their activation within other inflammatory environments that further aggravated their exhaustion. Our findings reveal that cDC1s maintain and safeguard Tpex cells within distinct anatomical niches to balance viral control, exhaustion, and immunopathology. [Display omitted] • Determined differentiation trajectory and location of Tex cells and their precursors • cDC1s are essential for viral control but not for Tpex cell expansion • cDC1s maintain Tpex cell niches in an MHC-I-dependent manner • cDC1s limit activation-driven T cell exhaustion and immunopathology Dähling et al. establish the role of cDCs for immunotherapy and find that cDC1s are required to mediate viral control. cDC1s provide a niche to maintain the precursors of exhausted T (Tpex) cell population and prevent their overactivation and subsequent immunopathology. These findings reveal the importance of cDC1s in maintaining Tpex cells to balance viral control, exhaustion, and immunopathology. [ABSTRACT FROM AUTHOR]

The tumor immune microenvironment plays a critical role in cancer progression and response to immunotherapy in clear cell renal cell carcinoma (ccRCC), yet the composition and phenotypic states of immune cells in this tumor are incompletely characterized. We performed single-cell RNA and T cell receptor sequencing on 164,722 individual cells from tumor and adjacent non-tumor tissue in patients with ccRCC across disease stages: early, locally advanced, and advanced/metastatic. Terminally exhausted CD8 + T cells were enriched in metastatic disease and were restricted in T cell receptor diversity. Within the myeloid compartment, pro-inflammatory macrophages were decreased, and suppressive M2-like macrophages were increased in advanced disease. Terminally exhausted CD8 + T cells and M2-like macrophages co-occurred in advanced disease and expressed ligands and receptors that support T cell dysfunction and M2-like polarization. This immune dysfunction circuit is associated with a worse prognosis in external cohorts and identifies potentially targetable immune inhibitory pathways in ccRCC., Competing Interests: Declaration of interests D.A.B. reports nonfinancial support from Bristol Myers Squibb, honoraria from LM Education/Exchange Services, and personal fees from Octane Global, Defined Health, Dedham Group, Adept Field Solutions, Slingshot Insights, Blueprint Partnerships, Charles River Associates, Trinity Group, and Insight Strategy, outside of the submitted work. S.H.G. has patents licensed to Novalgen Inc, outside of the submitted work. Z.B. reports nonfinancial support from Bristol Myers Squibb and Genentech/imCore. D.B.K. has acted as an advisor to and has received consulting fees from Neon Therapeutics and owns equity in Agenus, Armata pharmaceuticals, Breakbio, Biomarin Pharmaceutical, Bristol Myers Squibb, Celldex Therapeutics, Chinook Therapeutics, Editas Medicine, Exelixis, Gilead Sciences, IMV, Lexicon Pharmaceuticals, Moderna, and Regeneron Pharmaceuticals. K.M.M. reports research support from Bristol Myers Squibb. B.A.M. reports consulting fees from Bayer, Astellas, Astra Zeneca, Seattle Genetics, Dendreon, Calithera, Exelixis, Nektar, Pfizer, Janssen, Genentech, Eisai, and EMD Serono, and research support to DFCI from Bristol Myers Squibb, Calithera, Exelixis, Seattle Genetics. D.F.M. has received consulting fees from Bristol Myers Squibb, Pfizer, Merck, Alkermes, EMD Serono, Eli Lilly, Iovance, and Eisai, and research support from Bristol Myers Squibb, Merck, Genentech, Pfizer, Exelixis, X4 Pharma, and Alkermes. S.A.S. reports nonfinancial support from Bristol Myers Squibb outside the submitted work. S.A.S. previously advised and has received consulting fees from Neon Therapeutics. S.A.S. reports nonfinancial support from Bristol Myers Squibb, and equity in Agenus Inc., Agios Pharmaceuticals, Breakbio Corp., Bristol Myers Squibb, and Lumos Pharma, outside the submitted work. S.S. reported personal fees from Merck, AstraZeneca, Bristol Myers Squibb, CRISPR Therapeutics AG, AACR, and NCI, grants from Bristol Myers Squibb, AstraZeneca, Novartis, and Exelixis, and royalties from Biogenex. A.H.S. has patents/pending royalties on the PD-1 pathway from Roche and Novartis. A.H.S. is on advisory boards for Bicara, Janssen Immunology, Surface Oncology, Elstar, SQZ Biotechnologies, Elpiscience, Selecta, and Monopteros, and consults for Novartis. A.H.S. has received research funding from AbbVie, Novartis, Roche, UCB, Ipsen, Quark, and Merck. D.F.M. reports personal fees from Bristol Myers Squibb, Pfizer, Merck, Novartis, Exelixis, Array BioPharm, Genentech, Alkermes, Jounce Therapeutics, X4 Pharma, Peloton, EMD Serono, and Eli Lilly, and research support from Bristol Myers Squibb, Prometheus Laboratories, Merck, Genentech, Pfizer, Exelixis, Novartis, X4 Pharma, Alkermes, and Peloton. T.K.C. reports grants and personal fees from Astra Zeneca; personal fees from Bayer; grants and personal fees from Bristol Myers Squibb; personal fees from Cerulean; grants and personal fees from Eisai; personal fees from Foundation Medicine Inc.; grants and personal fees from Exelixis; grants and personal fees from Genentech; personal fees from Roche; grants and personal fees from GlaxoSmithKline; grants and personal fees from Merck, from Novartis, Peloton, and Pfizer; personal fees from Prometheus Labs; grants and personal fees from Corvus; personal fees from Ipsen; grants from Tracon; and grants from Astellas outside the submitted work. The other authors declare no potential conflicts of interest. C.J.W. is an equity holder of BioNTech., (Copyright © 2021 Elsevier Inc. All rights reserved.)

TCF-1 is a key transcription factor in progenitor exhausted CD8 T cells (Tex). Moreover, this Tex cell subset mediates responses to PD-1 checkpoint pathway blockade. However, the role of the transcription factor TCF-1 in early fate decisions and initial generation of Tex cells is unclear. Single-cell RNA sequencing (scRNA-seq) and lineage tracing identified a TCF-1+Ly108+PD-1+ CD8 T cell population that seeds development of mature Tex cells early during chronic infection. TCF-1 mediated the bifurcation between divergent fates, repressing development of terminal KLRG1Hi effectors while fostering KLRG1Lo Tex precursor cells, and PD-1 stabilized this TCF-1+ Tex precursor cell pool. TCF-1 mediated a T-bet-to-Eomes transcription factor transition in Tex precursors by promoting Eomes expression and drove c-Myb expression that controlled Bcl-2 and survival. These data define a role for TCF-1 in early-fate-bifurcation-driving Tex precursor cells and also identify PD-1 as a protector of this early TCF-1 subset. • scRNA-seq defines an effector versus exhausted Tex cell-fate decision • TCF-1 plays a central role in initially establishing Tex precursor cells • PD-1 supports the TCF-1+ Tex precursor cells at early phase of chronic infection • Eomes and c-Myb play key roles in Tex cell persistence downstream of TCF-1 The initiation of the T cell exhaustion program remains poorly understood. In this study, Chen et al. define an effector (Teff) versus exhausted (Tex) CD8 T cell binary-fate decision during chronic infection and find that TCF-1 supports the Tex precursor development by antagonizing Teff-like cell differentiation through multiple transcription factors. [ABSTRACT FROM AUTHOR]