The T helper 17 (Th17) cell pathway has been linked by genome-wide association studies to multiple autoimmune diseases. Identification of the genetic causes of primary immunodeficiency diseases ...revealed that Th17 cells are also critical in host immunity to mucocutaneous candida infections and Staphylococcus aureus. Therapeutic interventions with inhibitors of the different components of the pathway such as interleukin-12 (IL-12), IL-23, IL-17A, and IL-17RA have variably beneficial effects in psoriasis, Crohn’s disease, rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, non-infectious uveitis, and multiple sclerosis. Thus, whereas Th17 cells are protective against Candida albicans and to a lesser degree Staphylococcus aureus, they are pathogenic in many autoimmune diseases. Here, we compare and contrast the effects of human genetic mutations of and therapeutic interventions targeted at Th17 cell molecules. We discuss that although there are similarities when Th17 cell pathway molecules are modulated, each molecule has unique non-Th17 cell features that lead to different functional outcomes.
The T helper 17 (Th17) cell pathway has been linked by genome-wide association studies to multiple autoimmune diseases. Identification of the genetic causes of primary immunodeficiency diseases revealed that Th17 cells are also critical in host immunity to mucocutaneous candida infections and Staphylococcus aureus. Therapeutic interventions with inhibitors of the different components of the pathway such as interleukin-12 (IL-12), IL-23, IL-17A, and IL-17RA have variably beneficial effects in psoriasis, Crohn’s disease, rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, non-infectious uveitis, and multiple sclerosis. Thus, whereas Th17 cells are protective against Candida albicans and to a lesser degree Staphylococcus aureus, they are pathogenic in many autoimmune diseases. Here, we compare and contrast the effects of human genetic mutations of and therapeutic interventions targeted at Th17 cell molecules. We discuss that although there are similarities when Th17 cell pathway molecules are modulated, each molecule has unique non-Th17 cell features that lead to different functional outcomes.
Co-inhibitory receptors, such as CTLA-4 and PD-1, have an important role in regulating T cell responses and have proven to be effective targets in the setting of chronic diseases where constitutive ...co-inhibitory receptor expression on T cells dampens effector T cell responses. Unfortunately, many patients still fail to respond to therapies that target CTLA-4 and PD-1. The next wave of co-inhibitory receptor targets that are being explored in clinical trials include Lag-3, Tim-3, and TIGIT. These receptors, although they belong to the same class of receptors as PD-1 and CTLA-4, exhibit unique functions, especially at tissue sites where they regulate distinct aspects of immunity. Increased understanding of the specialized functions of these receptors will inform the rational application of therapies that target these receptors to the clinic.
The next wave of co-inhibitory receptor targets for immunotherapy has specialized roles in regulating diverse aspects of the immune response. Understanding these roles is critical for incorporating therapies against these receptors into the current immunotherapy landscape.
Summary
Immunotherapy is being increasingly recognized as a key therapeutic modality to treat cancer and represents one of the most exciting treatments for the disease. Fighting cancer with ...immunotherapy has revolutionized treatment for some patients and therapies targeting the immune checkpoint molecules such as CTLA‐4 and PD‐1 have achieved durable responses in melanoma, renal cancer, Hodgkin's diseases and lung cancer. However, the success rate of these treatments has been low and a large number of cancers, including colorectal cancer remain largely refractory to CTLA‐4 and PD‐1 blockade. This has provided impetus to identify other co‐inhibitory receptors that could be exploited to enhance response rates of current immunotherapeutic agents and achieve responses to the cancers that are refectory to immunotherapy. Tim‐3 is a co‐inhibitory receptor that is expressed on IFN‐g‐producing T cells, FoxP3+ Treg cells and innate immune cells (macrophages and dendritic cells) where it has been shown to suppress their responses upon interaction with their ligand(s). Tim‐3 has gained prominence as a potential candidate for cancer immunotherapy, where it has been shown that in vivo blockade of Tim‐3 with other check‐point inhibitors enhances anti‐tumor immunity and suppresses tumor growth in several preclinical tumor models. This review discusses the recent findings on Tim‐3, the role it plays in regulating immune responses in different cell types and the rationale for targeting Tim‐3 for effective cancer immunotherapy.
T cell immunoglobulin and mucin domain-containing protein 3 (TIM3), a member of the TIM family, was originally identified as a receptor expressed on interferon-γ-producing CD4
and CD8
T cells. ...Initial data indicated that TIM3 functioned as a 'co-inhibitory' or 'checkpoint' receptor, but due to the lack of a definable inhibitory signalling motif, it was also suggested that TIM3 might act as a co-stimulatory receptor. Recent studies have shown that TIM3 is part of a module that contains multiple co-inhibitory receptors (checkpoint receptors), which are co-expressed and co-regulated on dysfunctional or 'exhausted' T cells in chronic viral infections and cancer. Furthermore, co-blockade of TIM3 and programmed cell death 1 (PD1) can result in tumour regression in preclinical models and can improve anticancer T cell responses in patients with advanced cancers. Here, we highlight the developments in understanding TIM3 biology, including novel ligand identification and the discovery of loss-of-function mutations associated with human disease. In addition, we summarize emerging data from human clinical trials showing that TIM3 indeed acts as a 'checkpoint' receptor and that inhibition of TIM3 enhances the antitumour effect of PD1 blockade.
Foxp3+ T regulatory (Treg) cells regulate immune responses and maintain self-tolerance. Recent work shows that Treg cells are comprised of many subpopulations with specialized regulatory functions. ...Here we identified Foxp3+ T cells expressing the coinhibitory molecule TIGIT as a distinct Treg cell subset that specifically suppresses proinflammatory T helper 1 (Th1) and Th17 cell, but not Th2 cell responses. Transcriptional profiling characterized TIGIT+ Treg cells as an activated Treg cell subset with high expression of Treg signature genes. Ligation of TIGIT on Treg cells induced expression of the effector molecule fibrinogen-like protein 2 (Fgl2), which promoted Treg-cell-mediated suppression of T effector cell proliferation. In addition, Fgl2 was necessary to prevent suppression of Th2 cytokine production in a model of allergic airway inflammation. TIGIT expression therefore identifies a Treg cell subset that demonstrates selectivity for suppression of Th1 and Th17 cell but not Th2 cell responses.
•TIGIT defines a distinct Foxp3+ Treg cell subset•TIGIT induces transcription and secretion of the effector molecule Fgl2 in Treg cells•TIGIT+ Treg cells suppress proinflammatory Th1 and Th17 not Th2 cell responses•Selective suppression by TIGIT+ Treg cells is Fgl2 dependent
Ectopic lymphoid follicles are hallmarks of chronic autoimmune inflammatory diseases such as multiple sclerosis (MS), rheumatoid arthritis, Sjögren's syndrome, and myasthenia gravis. However, the ...effector cells and mechanisms that induce their development are unknown. Here we showed that in experimental autoimmune encephalomyelitis (EAE), the animal model of MS, Th17 cells specifically induced ectopic lymphoid follicles in the central nervous system (CNS). Development of ectopic lymphoid follicles was partly dependent on the cytokine interleukin 17 (IL-17) and on the cell surface molecule Podoplanin (Pdp), which was expressed on Th17 cells, but not on other effector T cell subsets. Pdp was also crucial for the development of secondary lymphoid structures: Pdp-deficient mice lacked peripheral lymph nodes and had a defect in forming normal lymphoid follicles and germinal centers in spleen and lymph node remnants. Thus, Th17 cells are uniquely endowed to induce tissue inflammation, characterized by ectopic lymphoid follicles within the target organ.
► Th17 cells but not other T cell subsets induce ectopic follicles in the CNS ► Th17 cells but not other T cell subsets express Podoplanin ► Formation of ectopic follicles depends on IL-17 and on Podoplanin ► Podoplanin is also crucial for formation of organized secondary lymphoid structures
Co-inhibitory receptors are important regulators of T-cell function that define the balance between tolerance and autoimmunity. The immune regulatory function of co-inhibitory receptors, including ...CTLA-4, PD-1, TIM-3, TIGIT, and LAG-3, was first discovered in the setting of autoimmune disease models, in which their blockade or deficiency resulted in induction or exacerbation of the disease. Later on, co-inhibitory receptors on lymphocytes have also been found to influence outcomes in tumor and chronic viral infection settings. These receptors suppress T-cell function in the tumor microenvironment (TME), thereby making the T cells dysfunctional. Based on this observation, blockade of co-inhibitory receptors (also known as checkpoint molecules) has emerged as a successful treatment option for a number of human cancers. However, severe autoimmune-like side effects limit the use of therapeutics that block individual or combinations of co-inhibitory receptors for cancer treatment. In this review we provide an overview of the role of co-inhibitory receptors in autoimmunity and anti-tumor immunity. We then discuss current approaches and future directions to leverage our knowledge of co-inhibitory receptors to target them in tumor immunity without inducing autoimmunity.
Interleukin-17 and type 17 helper T cells Miossec, Pierre; Korn, Thomas; Kuchroo, Vijay K
The New England journal of medicine,
08/2009, Letnik:
361, Številka:
9
Journal Article
T cell inhibitory co-receptors play a crucial role in maintaining the balance between physiologic immune responses and maladaptive ones. T cell immunoglobulin and mucin domain-containing-3 (Tim-3) is ...a unique inhibitory co-receptor in that its expression is chiefly restricted to interferon (IFN)γ-producing CD4+ and CD8+ T cells. Early reports firmly established its importance in maintaining peripheral tolerance in transplantation and autoimmunity. However, it has become increasingly clear that Tim-3 expression on T cells, together with other check-point molecules, in chronic infections and cancers can hinder productive immune responses. In this review, we outline what is currently known about the regulation of Tim-3 expression, its ligands and signaling. We discuss both its salutary and deleterious function in immune disorders, as well as the T cell-extrinsic and -intrinsic factors that regulate its function.
The β-galactoside-binding protein galectin-9 is critical in regulating the immune response, but the mechanism by which it functions remains unclear. We have demonstrated that galectin-9 is highly ...expressed by induced regulatory T cells (iTreg) and was crucial for the generation and function of iTreg cells, but not natural regulatory T (nTreg) cells. Galectin-9 expression within iTreg cells was driven by the transcription factor Smad3, forming a feed-forward loop, which further promoted Foxp3 expression. Galectin-9 increased iTreg cell stability and function by directly binding to its receptor CD44, which formed a complex with transforming growth factor-β (TGF-β) receptor I (TGF-βRI), and activated Smad3. Galectin-9 signaling was further found to regulate iTreg cell induction by dominantly acting through the CNS1 region of the Foxp3 locus. Our data suggest that exogenous galectin-9, in addition to being an effector molecule for Treg cells, acts synergistically with TGF-β to enforce iTreg cell differentiation and maintenance.
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•Galectin-9 enhances Foxp3 in iTregs, but not nTregs•Galectin-9 enhances iTregs function and stability•Galectin-9-CD44-TGF-βRI results in epigenetic modification at the Foxp3 locus•Smad3 drives galectin-9 expression, which further promotes Foxp3 expression in iTregs
Galectin-9 is crucial for the generation and function of induced regulatory T (iTreg) cells, but not natural Treg cells. Kuchroo and colleagues demonstrate that exogenous galectin-9 acts synergistically with TGF-β to enforce iTreg cell differentiation and maintenance.
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