Differential impact of TIM-3 ligands on NK cell function.

Background: The transmembrane protein T-cell immunoglobulin and mucin-domain containing molecule 3 (TIM-3) is an immune checkpoint receptor that is expressed by a variety of leukocyte subsets, particularly in the tumor microenvironment. An effective TIM-3-targeting therapy should account for multiple biological factors, including the disease setting, the specific cell types involved and their varying sensitivities to the four putative TIM-3 ligands (galectin-9, phosphatidylserine, high mobility group protein B1 and carcinoembryonic antigen cell adhesion molecule 1), each of which engages a unique binding site on the receptor's variable immunoglobulin domain. The primary objectives of this study were to assess the prevalence and function of TIM-3 natural killer (NK) cells in patients with head and neck squamous cell carcinoma (HNSCC), determine whether the four TIM-3 ligands differentially affect TIM-3 NK cell functions, identify the most immunosuppressive ligand, and evaluate whether targeting ligand-mediated TIM-3 signaling enhances NK cell effector functions.

Dysfunction of exhausted T cells is enforced by MCT11-mediated lactate metabolism.

CD8 T cells are critical mediators of antitumor immunity but differentiate into a dysfunctional state, known as T cell exhaustion, after persistent T cell receptor stimulation in the tumor microenvironment (TME). Exhausted T (T) cells are characterized by upregulation of coinhibitory molecules and reduced polyfunctionality. T cells in the TME experience an immunosuppressive metabolic environment via reduced levels of nutrients and oxygen and a buildup of lactic acid.

Downregulation of PIK3IP1/TrIP on T cells is controlled by TCR signal strength, PKC, and metalloprotease-mediated cleavage.

The protein known as PI3K-interacting protein (PIK3IP1), or transmembrane inhibitor of PI3K (TrIP), is highly expressed by T cells and can modulate PI3K activity in these cells. Several studies have also revealed that TrIP is rapidly downregulated following T cell activation. However, it is unclear how this downregulation is controlled.

Tim-3 Is Required for Regulatory T Cell-Mediated Promotion of T Cell Exhaustion and Viral Persistence during Chronic Lymphocytic Choriomeningitis Virus Infection.

Expression of T cell Ig and mucin domain-containing protein 3 (Tim-3) is upregulated on regulatory T cells (Tregs) during chronic viral infections. In several murine and human chronic infections, the expression of Tim-3 is associated with poor control of viral burden and impaired antiviral immune responses. However, the role of Tim-3+ Tregs during persistent viral infections has not been fully defined.

TIM-3 on myeloid cells promotes pulmonary inflammation through increased production of galectin-3.

T cell immunoglobulin and mucin-containing molecule 3 (TIM-3) exhibits unique, cell type- and context-dependent characteristics and functions. Here, we report that TIM-3 on myeloid cells plays essential roles in modulating lung inflammation. We found that myeloid cell-specific TIM-3 knock-in (FSF-TIM3/LysM-Cre) mice have lower body weight and shorter lifespan than WT mice.

Downregulation of PIK3IP1/TrIP on T cells is controlled by TCR signal strength, PKC and metalloprotease-mediated cleavage.

The protein known as PI3K-interacting protein (PIK3IP1), or transmembrane inhibitor of PI3K (TrIP), is highly expressed by T cells and can modulate PI3K activity in these cells. Several studies have also revealed that TrIP is rapidly downregulated following T cell activation. However, it is unclear as to how this downregulation is controlled.

Tim-3 Is Not Required for Establishment of CD8+ T Cell Memory to Lymphocytic Choriomeningitis Virus.

Tim-3 is a transmembrane protein that is best known for being highly expressed on terminally exhausted CD8+ T cells associated with chronic infection and tumors, although its expression is not limited to those settings. Tim-3 is also expressed by CD8+ T cells during acute infection and by multiple other immune cell types, including CD4+ Th1 and regulatory T cells, dendritic cells, and mast cells. In this study, we investigated the role of Tim-3 signaling on CD8+ T cell memory using a Tim-3 conditional knockout mouse model and mice lacking the signaling portion of the Tim-3 cytoplasmic domain.

Complementary HLH susceptibility factors converge on CD8 T-cell hyperactivation.

Hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are life-threatening hyperinflammatory syndromes. Familial HLH is caused by genetic impairment of granule-mediated cytotoxicity (eg, perforin deficiency). MAS is linked to excess activity of the inflammasome-activated cytokine interleukin-18 (IL-18).

TIM-3 signaling contributes to the suppressive capacity of Tregs from people with HIV on antiretroviral therapy.

TIM-3 expression is increased on peripheral regulatory T cells (Tregs) of virally suppressed persons with HIV-1 on antiretroviral therapy (PWH-ART). However, the relevance of TIM-3 expression in this setting is unclear. We used flow cytometry to evaluate the suppressive phenotype and signaling pathways in peripheral TIM-3- vs TIM-3+ Tregs in PWH-ART.

Tissue-resident memory T cell maintenance during antigen persistence requires both cognate antigen and interleukin-15.

Our understanding of tissue-resident memory T (T) cell biology has been largely developed from acute infection models in which antigen is cleared and sterilizing immunity is achieved. Less is known about T cells in the context of chronic antigen persistence and inflammation. We investigated factors that underlie T maintenance in a kidney transplantation model in which T cells drive rejection.

Tim-3 mediates T cell trogocytosis to limit antitumor immunity.

T cell immunoglobulin mucin domain-containing protein 3 (Tim-3) negatively regulates innate and adaptive immunity in cancer. To identify the mechanisms of Tim-3 in cancer immunity, we evaluated the effects of Tim-3 blockade in human and mouse melanoma. Here, we show that human programmed cell death 1-positive (PD-1+) Tim-3+CD8+ tumor-infiltrating lymphocytes (TILs) upregulate phosphatidylserine (PS), a receptor for Tim-3, and acquire cell surface myeloid markers from antigen-presenting cells (APCs) through transfer of membrane fragments called trogocytosis.

Regulation of Tim-3 function by binding to phosphatidylserine.

Tim-3 is a transmembrane protein that is highly expressed on subsets of chronically stimulated CD4+ helper and CD8+ cytotoxic T cells, with more transient expression during acute activation and infection. Tim-3 is also constitutively expressed by multiple types of myeloid cells. Like other TIM family members, Tim-3 can bind to phosphatidylserine displayed by apoptotic cells, and this interaction has been shown to mediate uptake of such cells by dendritic cells and cross-presentation of antigens to CD8+ T cells.

Expression of Tim-3 drives phenotypic and functional changes in Treg cells in secondary lymphoid organs and the tumor microenvironment.

Regulatory T cells (Treg cells) are critical mediators of self-tolerance, but they can also limit effective anti-tumor immunity. Although under homeostasis a small fraction of Treg cells in lymphoid organs express the putative checkpoint molecule Tim-3, this protein is expressed by a much larger proportion of tumor-infiltrating Treg cells. Using a mouse model that drives cell-type-specific inducible Tim-3 expression, we show that expression of Tim-3 by Treg cells is sufficient to drive Treg cells to a more effector-like phenotype, resulting in increases in suppressive activity, effector T cell exhaustion, and tumor growth.

The costimulatory activity of Tim-3 requires Akt and MAPK signaling and its recruitment to the immune synapse.

Expression of the transmembrane protein Tim-3 is increased on dysregulated T cells undergoing chronic activation, including during chronic infection and in solid tumors. Thus, Tim-3 is generally thought of as an inhibitory protein. We and others previously reported that under some circumstances, Tim-3 exerts paradoxical costimulatory activity in T cells (and other cells), including enhancement of the phosphorylation of ribosomal S6 protein.

Association of Mast Cell Burden and TIM-3 Expression with Recalcitrant Chronic Rhinosinusitis with Nasal Polyps.

Objectives: Previous work showed that higher polyp mast cell load correlated with worse postoperative endoscopic appearance in patients with chronic rhinosinusitis with nasal polyps (CRSwNP). Polyp epithelial mast cells showed increased expression of T-cell/transmembrane immunoglobulin and mucin domain protein 3 (TIM-3), a receptor that promotes mast cell activation and cytokine production. In this study, CRSwNP patients were followed post-operatively to investigate whether mast cell burden or TIM-3 expression among mast cells can predict recalcitrant disease.

Control of T lymphocyte fate decisions by PI3K signaling.

Virtually all aspects of T and B lymphocyte development, homeostasis, activation, and effector function are impacted by the interaction of their clonally distributed antigen receptors with antigens encountered in their respective environments. Antigen receptors mediate their effects by modulating intracellular signaling pathways that ultimately impinge on the cytoskeleton, bioenergetic pathways, transcription, and translation. Although these signaling pathways are rather well described at this point, especially those steps that are most receptor-proximal, how such pathways contribute to more quantitative aspects of lymphocyte function is still being elucidated.

PIK3IP1 Promotes Extrafollicular Class Switching in T-Dependent Immune Responses.

PI3K plays multiple roles throughout the life of a B cell. As such, its signaling is tightly regulated. The importance of this is illustrated by the fact that both loss- and gain-of-function mutations in PI3K can cause immunodeficiency in humans.

Noncanonical STAT3 activity sustains pathogenic Th17 proliferation and cytokine response to antigen.

The STAT3 signaling pathway is required for early Th17 cell development, and therapies targeting this pathway are used for autoimmune disease. However, the role of STAT3 in maintaining inflammatory effector Th17 cell function has been unexplored. Th17ΔSTAT3 mice, which delete STAT3 in effector Th17 cells, were resistant to experimental autoimmune encephalomyelitis (EAE), a murine model of MS.

Glial TIM-3 Modulates Immune Responses in the Brain Tumor Microenvironment.

T-cell immunoglobulin and mucin domain-containing molecule 3 (TIM-3), a potential immunotherapeutic target for cancer, has been shown to display diverse characteristics in a context-dependent manner. Thus, it would be useful to delineate the precise functional features of TIM-3 in a given situation. Here, we report that glial TIM-3 shows distinctive properties in the brain tumor microenvironment.

Differential Expression of Immune Checkpoint Molecules on CD8 T Cells Specific for Immunodominant and Subdominant Herpes Simplex Virus 1 Epitopes.

Herpes simplex virus 1 (HSV-1) causes a lifelong infection of neurons that innervate barrier sites like the skin and mucosal surfaces like the eye. After primary infection of the cornea, the virus enters latency within the trigeminal ganglion (TG), from which it can reactivate throughout the life of the host. Viral latency is maintained, in part, by virus-specific CD8 T cells that nonlethally interact with infected neurons.

A predicted DXD-motif glycosyltransferase blocks immune activation.

Pathogens enhance their survival during infections by manipulating host defenses. evades innate immune responses, which we have found to be dependent on an understudied gene (FTL_0883/FTT_0615c). To understand the function of YbeX, we sought protein interactors in subsp.

The Alzheimer's Disease-Associated Protein BACE1 Modulates T Cell Activation and Th17 Function.

β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) is best known for its role in Alzheimer's disease amyloid plaque formation but also contributes to neurodegenerative processes triggered by CNS injury. In this article, we report that BACE1 is expressed in murine CD4 T cells and regulates signaling through the TCR. BACE1-deficient T cells have reduced IL-17A expression under Th17 conditions and reduced CD73 expression in Th17 and inducible T regulatory cells.

PIK3IP1/TrIP restricts activation of T cells through inhibition of PI3K/Akt.

Phosphatidylinositol-3 kinases (PI3Ks) modulate cellular growth, proliferation, and survival; dysregulation of the PI3K pathway can lead to autoimmune disease and cancer. PIK3IP1 (or transmembrane inhibitor of PI3K [TrIP]) is a putative transmembrane regulator of PI3K. TrIP contains an extracellular kringle domain and an intracellular domain with homology to the inter-SH2 domain of the PI3K regulatory subunit p85, but the mechanism of TrIP function is poorly understood.

Kidney-infiltrating T cells in murine lupus nephritis are metabolically and functionally exhausted.

While T cells are important for the pathogenesis of systemic lupus erythematosus (SLE) and lupus nephritis, little is known about how T cells function after infiltrating the kidney. The current paradigm suggests that kidney-infiltrating T cells (KITs) are activated effector cells contributing to tissue damage and ultimately organ failure. Herein, we demonstrate that the majority of CD4+ and CD8+ KITs in 3 murine lupus models are not effector cells, as hypothesized, but rather express multiple inhibitory receptors and are highly dysfunctional, with reduced cytokine production and proliferative capacity.