Search

T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3) is an important immune checkpoint molecule initially identified as a marker of IFN-γ–producing CD4+ and CD8+ T cells. Since then, our understanding of its role in immune responses has significantly expanded. Here, we review emerging evidence demonstrating unexpected roles for TIM-3 as a key regulator of myeloid cell function, in addition to recent work establishing TIM-3 as a delineator of terminal T cell exhaustion, thereby positioning TIM-3 at the interface between fatigued immune responses and reinvigoration. We share our perspective on the antagonism between TIM-3 and T cell stemness, discussing both cell-intrinsic and cell-extrinsic mechanisms underlying this relationship. Looking forward, we discuss approaches to decipher the underlying mechanisms by which TIM-3 regulates stemness, which has remarkable potential for the treatment of cancer, autoimmunity, and autoinflammation. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) sense environmental cues and adopt either an immune-stimulatory or regulatory phenotype, thereby fine-tuning immune responses. Identifying endogenous regulators that determine DC function can thus inform the development of therapeutic strategies for modulating the immune response in different disease contexts. Tim-3 plays an important role in regulating immune responses by inhibiting the activation status and the T cell priming ability of DC in the setting of cancer. Bat3 is an adaptor protein that binds to the tail of Tim-3; therefore, we studied its role in regulating the functional status of DCs. In murine models of autoimmunity (experimental autoimmune encephalomyelitis) and cancer (MC38-OVA–implanted tumor), lack of Bat3 expression in DCs alters the T cell compartment—it decreases TH1, TH17 and cytotoxic effector cells, increases regulatory T cells, and exhausted CD8+ tumor-infiltrating lymphocytes, resulting in the attenuation of autoimmunity and acceleration of tumor growth. We found that Bat3 expression levels were differentially regulated by activating versus inhibitory stimuli in DCs, indicating a role for Bat3 in the functional calibration of DC phenotypes. Mechanistically, loss of Bat3 in DCs led to hyperactive unfolded protein response and redirected acetyl–coenzyme A to increase cell intrinsic steroidogenesis. The enhanced steroidogenesis in Bat3-deficient DC suppressed T cell response in a paracrine manner. Our findings identified Bat3 as an endogenous regulator of DC function, which has implications for DC-based immunotherapies. [ABSTRACT FROM AUTHOR]

Leukemia relapse is a major cause of death after allogeneic hematopoietic cell transplantation (allo-HCT). We tested the potential of targeting T cell (Tc) immunoglobulin and mucin-containing molecule 3 (TIM-3) for improving graft-versus-leukemia (GVL) effects. We observed differential expression of TIM-3 ligands when hematopoietic stem cells overexpressed certain oncogenic-driver mutations. Anti--TIM-3 Ab treatment improved survival of mice bearing leukemia with oncogene-induced TIM- 3 ligand expression. Conversely, leukemia cells with low ligand expression were anti--TIM-3 treatment resistant. In vitro, TIM-3 blockade or genetic deletion in CD8+ Tc enhanced Tc activation, proliferation, and IFN-γ production while enhancing GVL effects, preventing Tc exhaustion, and improving Tc cytotoxicity and glycolysis in vivo. Conversely, TIM-3 deletion in myeloid cells did not affect allogeneic Tc proliferation and activation in vitro, suggesting that anti--TIM-3 treatment--mediated GVL effects are Tc induced. In contrast to anti--programmed cell death protein 1 (anti--PD-1) and anti--cytotoxic T lymphocyte--associated protein 4 (anti--CTLA-4) treatment, anti--TIM-3-treatment did not enhance acute graft-versus-host disease (aGVHD). TIM-3 and its ligands were frequently expressed in acute myeloid leukemia (AML) cells of patients with post--allo-HCT relapse. We decipher the connections between oncogenic mutations found in AML and TIM-3 ligand expression and identify anti--TIM-3 treatment as a strategy for enhancing GVL effects via metabolic and transcriptional Tc reprogramming without exacerbation of aGVHD. Our findings support clinical testing of anti--TIM-3 Ab in patients with AML relapse after allo-HCT. [ABSTRACT FROM AUTHOR]

Coinhibitory receptors, such as CTLA-4 and PD-1, play a critical role in maintaining immune homeostasis by dampening T cell responses. Recently, they have gained attention as therapeutic targets in chronic disease settings where their dysregulated expression contributes to suppressed immune responses. The novel coinhibitory receptor TIGIT (T cell Ig and ITIM domain) has been shown to play an important role in modulating immune responses in the context of autoimmunity and cancer. However, the molecular mechanisms by which TIGIT modulates immune responses are still insufficiently understood. We have generated a panel of monoclonal anti-mouse TIGIT Abs that show functional properties in mice in vivo and can serve as important tools to study the underlying mechanisms of TIGIT function. We have identified agonistic as well as blocking anti-TIGITAb clones that are capable of modulating T cell responses in vivo. Administration of either agonist or blocking anti-TIGIT Abs modulated autoimmune disease severity whereas administration of blocking anti-TIGIT Abs synergized with anti-PD-1 Abs to affect partial or even complete tumor regression. The Abs presented in this study can thus serve as important tools for detailed analysis of TIGIT function in different disease settings and the knowledge gained will provide valuable insight for the development of novel therapeutic approaches targeting TIGIT. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) and complement are both key members of the innate and adaptive immune response. Recent experimental mouse models have shown that production of alternative pathway (AP) components by DCs strongly affects their ability to activate and regulate T-cell responses. In this study we investigated the production and regulation of properdin (fP) and factor H (fH) both integral regulators of the AP, by DCs and tolerogenic DCs (tolDCs). Both fP and fH were produced by DCs, with significantly higher levels of both AP components produced by tolDCs. Upon activation with IFN-γ both cells increased fH production, while simultaneously decreasing production of fP. IL-27, a member of the IL-12 family, increased fH, but production of fP remained unaffected. The functional capacity of fP and fH produced by DCs and tolDCs was confirmed by their ability to bind C3b. Inhibition of fH production by DCs resulted in a greater ability to induce allogenic CD4+ T-cell proliferation. In contrast, inhibition of fP production led to a significantly reduced allostimulatory capacity. In summary, this study shows that production of fP and fH by DCs, differentially regulates their immunogenicity, and that the local cytokine environment can profoundly affect the production of fP and fH. [ABSTRACT FROM AUTHOR]

Previous studies have shown that complement activation on renal tubular cells is involved in the induction of interstitial fibrosis and cellular injury. Evidence suggests that the tubular cell damage is initiated by the alternative pathway (AP) of complement with properdin having an instrumental role. Properdin is a positive regulator of the AP, which can bind necrotic cells as well as viable proximal tubular epithelial cells (PTECs), inducing complement activation. Various studies have indicated that in the circulation there is an unidentified inhibitor of properdin. We investigated the ability of C-reactive protein (CRP), both in its monomeric (mCRP) and pentameric (pCRP) form, to inhibit AP activation and injury in vitro on renal tubular cells by fluorescent microscopy, ELISA, and flow cytometry. We demonstrated that preincubation of properdin with normal human serum inhibits properdin binding to viable PTECs. We identified mCRP as a factor able to bind to properdin in solution, thereby inhibiting its binding to PTECs. In contrast, pCRP exhibited no such binding and inhibitory effect. Furthermore, mCRP was able to inhibit properdindirected C3 and C5b-9 deposition on viable PTECs. The inhibitory ability of mCRP was not unique for viable cells but also demonstrated for binding to necrotic Jurkat cells, a target for properdin binding and complement activation. In summary, mCRP is an inhibitor of properdin in both binding to necrotic cells and viable renal cells, regulating complement activation on the cell surface. We propose that mCRP limits amplification of tissue injury by controlling properdin-directed complement activation by damaged tissue and cells. [ABSTRACT FROM AUTHOR]

Summary: The field of cancer neuroscience has begun to define the contributions of nerves to cancer initiation and progression; here, we highlight the future directions of basic and translational cancer neuroscience for malignancies arising outside of the central nervous system., (©2024 American Association for Cancer Research.)

Background: Although immune checkpoint inhibitors have been a breakthrough in clinical oncology, these therapies fail to produce durable responses in a significant fraction of patients. This lack of long-term efficacy may be due to a poor pre-existing network linking innate and adaptive immunity. Here, we present an antisense oligonucleotide (ASO)-based strategy that dually targets toll-like receptor 9 (TLR9) and programmed cell death ligand 1 (PD-L1), aiming to overcome resistance to anti-PD-L1 monoclonal therapy., Methods: We designed a high-affinity immunomodulatory IM-TLR9:PD-L1-ASO antisense oligonucleotide (hereafter, IM-T9P1-ASO) targeting mouse PD-L1 messenger RNA and activating TLR9. Then, we performed in vitro and in vivo studies to validate the IM-T9P1-ASO activity, efficacy, and biological effects in tumors and draining lymph nodes. We also performed intravital imaging to study IM-T9P1-ASO pharmacokinetics in the tumor., Results: IM-T9P1-ASO therapy, unlike PD-L1 antibody therapy, results in durable antitumor responses in multiple mouse cancer models. Mechanistically, IM-T9P1-ASO activates a state of tumor-associated dendritic cells (DCs), referred to here as DC3s, which have potent antitumor potential but express the PD-L1 checkpoint. IM-T9P1-ASO has two roles: it triggers the expansion of DC3s by engaging with TLR9 and downregulates PD-L1, thereby unleashing the antitumor functions of DC3s. This dual action leads to tumor rejection by T cells. The antitumor efficacy of IM-T9P1-ASO depends on the antitumor cytokine interleukin-12 (IL-12), produced by DC3s, and Batf3 , a transcription factor required for DC development., Conclusions: By simultaneously targeting TLR9 and PD-L1, IM-T9P1-ASO amplifies antitumor responses via DC activation, leading to sustained therapeutic efficacy in mice. By highlighting differences and similarities between mouse and human DCs, this study could serve to develop similar therapeutic strategies for patients with cancer., Competing Interests: Competing interests: AZ received consulting/advisor fees from BMS, MSD, Hoffmann–La Roche, NBE Therapeutics, Secarna, ACM Pharma, and Hookipa, and maintains further non-commercial research agreements with Secarna, Hookipa, and Beyondsprings. MP has served as a consultant for Aileron Therapeutics, AstraZeneca, Cygnal Therapeutics, Elstar Therapeutics, ImmuneOncia, KSQ Therapeutics, Merck, Siamab Therapeutics, and Third Rock Ventures. The wife of RB is an employee and shareholder of CSL Behring and RB received speakers fee from Janssen. RHK, JF, AM, and FJ are employed by Secarna. CC is currently employed by Idorsia Pharmaceuticals., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Dendritic cells (DCs) sense environmental cues and adopt either an immune-stimulatory or regulatory phenotype, thereby fine-tuning immune responses. Identifying endogenous regulators that determine DC function can thus inform the development of therapeutic strategies for modulating the immune response in different disease contexts. Tim-3 plays an important role in regulating immune responses by inhibiting the activation status and the T cell priming ability of DC in the setting of cancer. Bat3 is an adaptor protein that binds to the tail of Tim-3; therefore, we studied its role in regulating the functional status of DCs. In murine models of autoimmunity (experimental autoimmune encephalomyelitis) and cancer (MC38-OVA-implanted tumor), lack of Bat3 expression in DCs alters the T cell compartment-it decreases T H 1, T H 17 and cytotoxic effector cells, increases regulatory T cells, and exhausted CD8 + tumor-infiltrating lymphocytes, resulting in the attenuation of autoimmunity and acceleration of tumor growth. We found that Bat3 expression levels were differentially regulated by activating versus inhibitory stimuli in DCs, indicating a role for Bat3 in the functional calibration of DC phenotypes. Mechanistically, loss of Bat3 in DCs led to hyperactive unfolded protein response and redirected acetyl-coenzyme A to increase cell intrinsic steroidogenesis. The enhanced steroidogenesis in Bat3-deficient DC suppressed T cell response in a paracrine manner. Our findings identified Bat3 as an endogenous regulator of DC function, which has implications for DC-based immunotherapies.

T cell exhaustion has been associated with poor prognosis in persistent viral infection and cancer. Conversely, in the context of autoimmunity, T cell exhaustion has been favorably correlated with long-term clinical outcome. Understanding the development of exhaustion in autoimmune settings may provide underlying principles that can be exploited to quell autoreactive T cells. Here, we demonstrate that the adaptor molecule Bat3 acts as a molecular checkpoint of T cell exhaustion, with deficiency of Bat3 promoting a profound exhaustion phenotype, suppressing autoreactive T cell-mediated neuroinflammation. Mechanistically, Bat3 acts as a critical mTORC2 inhibitor to suppress Akt function. As a result, Bat3 deficiency leads to increased Akt activity and FoxO1 phosphorylation, indirectly promoting Prdm1 expression. Transcriptional analysis of Bat3 -/- T cells revealed up-regulation of dysfunction-associated genes, concomitant with down-regulation of genes associated with T cell effector function, suggesting that absence of Bat3 can trigger T cell dysfunction even under highly proinflammatory autoimmune conditions., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

Identifying signals in the tumor microenvironment (TME) that shape CD8 + T cell phenotype can inform novel therapeutic approaches for cancer. Here, we identified a gradient of increasing glucocorticoid receptor (GR) expression and signaling from naïve to dysfunctional CD8 + tumor-infiltrating lymphocytes (TILs). Conditional deletion of the GR in CD8 + TILs improved effector differentiation, reduced expression of the transcription factor TCF-1, and inhibited the dysfunctional phenotype, culminating in tumor growth inhibition. GR signaling transactivated the expression of multiple checkpoint receptors and promoted the induction of dysfunction-associated genes upon T cell activation. In the TME, monocyte-macrophage lineage cells produced glucocorticoids and genetic ablation of steroidogenesis in these cells as well as localized pharmacologic inhibition of glucocorticoid biosynthesis improved tumor growth control. Active glucocorticoid signaling associated with failure to respond to checkpoint blockade in both preclinical models and melanoma patients. Thus, endogenous steroid hormone signaling in CD8 + TILs promotes dysfunction, with important implications for cancer immunotherapy., Competing Interests: Declaration of Interests A.C.A. is a member of the SAB for Tizona Therapeutics, Compass Therapeutics, Zumutor Biologics, and Astellas Global Pharma Development, which have interests in cancer immunotherapy. V.K.K. is a member of the SAB for Astellas Global Pharma Development and has an ownership interest and is a member of the SAB for Tizona Therapeutics. A.R. and V.K.K. are co-founders of and have an ownership interest in Celsius Therapeutics. A.C.A.’s and V.K.K.’s interests were reviewed and managed by the Brigham and Women’s Hospital and Partners Healthcare in accordance with their conflict of interest policies. M.B. is a consultant for Eli Lilly and Company. A.R. is also an SAB member for Thermo Fisher, Neogene Therapeutics, Asimov, and Syros Pharmaceuticals and is an equity holder in Immunitas. A.R.’s interests were reviewed and managed by the Broad Institute and HHMI in accordance with their conflict of interest policies. A provisional patent application was filed including work in this manuscript., (Copyright © 2020 Elsevier Inc. All rights reserved.)

IL-35 is a cytokine of the IL-12 family, existing as a heterodimer of IL-12p35 and Ebi3. IL-35 has anti-inflammatory properties and is produced by regulatory T cells in humans and mice, where it is required for optimal suppression of immune responses. Distinct from other IL-12 cytokines, the expression of IL-35 has not been described in antigen-presenting cells. In view of the immune-regulatory properties of IL-35, we investigated the expression, regulation, and function of IL-12p35 and Ebi3 in human monocyte-derived dendritic cells and tolerogenic DCs (tolDCs). These tolDCs do not produce IL-12p70 or the homodimer IL-12p40. We demonstrate that tolDCs completely lack transcriptional expression of IL-12p40. However, tolDCs maintain mRNA expression of IL-12p35 and Ebi3. Using intracellular flow cytometry and Western blot analysis, we show that tolDCs produce Ebi3 and IL-12p35, and both can be enhanced upon stimulation with IFN-γ, LPS, or CD40L. tolDCs supernatants have the capacity to suppress T-cell activation. Using IL12A silencing, we demonstrate that IL-12p35 is required for tolDCs to reach their full suppressive potential. Taken together, our results indicate that tolDCs produce IL-35, providing an additional novel mechanism by which tolDCs elicit their tolerogenic potential., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Uptake of apoptotic cells by DCs is considered to contribute to induction and maintenance of immunological tolerance. TolDCs are sought after as cellular therapy in transplantation and autoimmunity and can be generated in vitro using GCs. In this study, we investigated how uptake of dead cells affects the production and expression of different members of the IL-12 family by immature DCs or TolDCs. We show that compared to regular immature DCs, TolDCs display elevated levels of PS-recognizing bridge molecule receptors αvβ5 and CD36, and have enhanced phagocytic abilities with accelerated uptake of apoptotic cells. We confirm that apoptotic cell uptake results in diminished production of IL-12p40 and IL-12p70 by DCs. We now show that this also results in increased expression of IL-12p35 and Ebi3. TolDCs completely lack expression of IL-12p40 yet have enhanced levels of Ebi3 and IL-12p35. Uptake by TolDCs of apoptotic or necrotic cells does not affect the expression of Ebi3/IL-12p35 and also does not increase IL-12p40. This is distinct from the culture of immature DCs with necrotic cells, which is sufficient to induce IL-12p40 secretion. Conversely, ingestion of apoptotic cells by DCs leads to increased expression of IL-12p35 and Ebi3 without affecting IL-12p40. In conclusion, we have shown that uptake of apoptotic versus necrotic cells by DCs differentially regulates members of the IL-12 family. Apoptotic cells favor expression of Ebi3 and IL-12p35, and we propose that differential regulation of the IL-12 family is an additional mechanism in determining the immune response to dying cells., (© 2014 Society for Leukocyte Biology.)