Treg cells: patrolling a dangerous neighborhood

Monitoring regulatory T cells as a prognostic marker in lung transplantation

Lung transplantation is the major surgical procedure, which restores normal lung functioning and provides years of life for patients suffering from major lung diseases. Lung transplant recipients are at high risk of primary graft dysfunction, and chronic lung allograft dysfunction (CLAD) in the form of bronchiolitis obliterative syndrome (BOS). Regulatory T cell (Treg) suppresses effector cells and clinical studies have demonstrated that Treg levels are altered in transplanted lung during BOS progression as compared to normal lung. Here, we discuss levels of Tregs/FOXP3 gene expression as a crucial prognostic biomarker of lung functions during CLAD progression in clinical lung transplant recipients. The review will also discuss Treg mediated immune tolerance, tissue repair, and therapeutic strategies for achieving in-vivo Treg expansion, which will be a potential therapeutic option to reduce inflammation-mediated graft injuries, taper the toxic side effects of ongoing immunosuppressants, and improve lung transplant survival rates.

Upregulation of EMID1 Accelerates to a Favorable Prognosis and Immune Infiltration in Lung Adenocarcinoma

Lung cancer is a difficult-to-treat cancer. Lung adenocarcinoma (LUAD) is the main subtype of lung cancer. Although there are many ways to treat lung cancer, the survival rate of patients is low. Therefore, novel molecules need to be identified to diagnose and treat LUAD. This study utilized The Cancer Genome Atlas (TCGA) LUAD data to analyze and validate the value of EMID1 as a LUAD diagnostic surface marker and overall survival prognostic marker. Differential expression analysis formally confirmed that decreased EMID1 expression was significantly associated with advanced stage and metastasis of lung cancer. Kaplan–Meier survival analysis showed that the patients with low EMID expression are dismal. The relationship between clinicopathological features and EMID1 was scored using Wilcoxon signed-rank test and R (v.3.5.1) logistic regression and suggested that patients with low EMID1 expression had a worse prognosis than patients with high EMID1 expression. (Gene Ontology) GO, Kyoto Encyclopedia of Genes and Genomes(KEGG), and gene set enrichment analysis (GSEA) were performed to investigate the potential mechanism of EMID1 expression on the prognosis of LUAD and suggested that Notch signaling pathway may be an important biological pathway for EMID1 to play a role in LUAD. Further, combined with univariate and multivariate Cox regression analysis, it was speculated that high and low levels of EMID1 expression and the logistic regression analysis of related clinical variables had significant clinical significance to verify the underlying mechanism of LUAD focus and prognosis. EMID1 plays an important role in the immune milieu of LUAD. Meanwhile, the correlation between tumor-infiltrating immune cells and genes was assessed using CIBERSORT, and it was found that the level of B cell infiltration was positively correlated with the expression of EMID1, all of which were validated in the GEO and GEPIA databases. In all, this study helps to understand the immune microenvironment of LUAD and improve the survival of patients with LUAD. Thus, EMID1 may be a novel immune-related prognostic marker of LUAD.

Structural Biology of the Tumor Microenvironment

Cancers can be described as "rogue organs" (Balkwill FR, Capasso M, Hagemann T, J Cell Sci 125:5591-5596, 2012) because they are composed of multiple cell types and tissues. The transformed cells can recruit and alter healthy cells from surrounding tissues for their own benefit. It is these interactions that create the tumor microenvironment (TME). The TME describes the cells, factors, and extracellular matrix proteins that make up the tumor and the area around it; the biology of the TME influences tumor progression. Changes in the TME can lead to the growth and development of the tumor, the death of the tumor, or tumor metastasis. Metastasis is the process by which cancer spreads from its initial site to a different part of the body. Metastasis occurs when cancer cells enter the circulatory system or lymphatic system after they break away from a tumor. Once the cells leave, they can travel to a different part of the body and form new tumors. Therefore, understanding the TME is critical to fully understand cancer and find a way to successfully combat it. Knowledge of the TME can better inform researchers of the ability of potential therapies to reach tumor cells. It can also give researchers potential targets to kill the tumor. Instead of directly killing the cancer cells, therapies can target an aspect of the TME which could then halt tumor development or lead to tumor death. In other cases, targeting another aspect of the TME could make it easier for another therapy to kill the cancer cells, for example, using nanoparticles with collagenases to target the collagen in the surrounding environment to expose the cancer cells to drugs (Zinger A, et al, ACS Nano 13(10):11008-11021, 2019).The TME can be split simply into cells and the structural matrix. Within these groups are fibroblasts, structural proteins, immune cells, lymphocytes, bone marrow-derived inflammatory cells, blood vessels, and signaling molecules (Spill F, et al, Curr Opin Biotechnol 40:41-48, 2016; Del Prete A, et al, Curr Opin Pharmacol 35:40-47, 2017; Arneth B, Medicina (Kaunas) 56(1), 2019). From structure to providing nutrients for growth, each of these components plays a critical role in tumor maintenance. Together these components impact cancer growth, development, and resistance to therapies (Hanahan D, Coussens LM, Cancer Cell 21:309-322, 2012). In this chapter, we will describe the TME and express the importance of the cellular and structural elements of the TME.

The hallmarks of ovarian cancer: Focus on angiogenesis and micro-environment and new models for their characterisation

Cancers develop by sustained growth, migration and invasion properties of tumour cells, supported by complex interactions with stromal cells within the tumour micro-environment. This review is focused on the latest discoveries regarding the highlighted role of angiogenesis and tumour micro-environment in ovarian cancer. This cancer milieu encompasses non-cancerous cells present in the tumour or nearby, including vessel-forming cells, fibroblasts and immune cells amongst others that work in a cooperative way with cancer cells, impacting tumour behaviour. Angiogenesis, migration and invasion, and more recently immune evasion, are cancer hallmarks clearly dependent on these supporting cells. Moreover, these stromal cells are more genetically stable than tumour cells and thus represent an attractive therapeutic target. A better understanding of the stromal cells function, and their complex interplay with cancer cells, will open additional areas to target, as the tumour-host interface.

Hyaluronan in the Tumor Microenvironment

The extracellular matrix is part of the microenvironment and its functions are associated with the physical and chemical properties of the tissue. Among the extracellular components, the glycosaminoglycan hyaluronan is a key component, defining both the physical and biochemical characteristics of the healthy matrices. The hyaluronan metabolism is strictly regulated in physiological conditions, but in the tumoral tissues, its expression, size and binding proteins interaction are dysregulated. Hyaluronan from the tumor microenvironment promotes tumor cell proliferation, invasion, immune evasion, stemness alterations as well as drug resistance. This chapter describes data regarding novel concepts of hyaluronan functions in the tumor. Additionally, we discuss potential clinical applications of targeting HA metabolism in cancer therapy.

Effects of Inhaled Tobacco Smoke on the Pulmonary Tumor Microenvironment

Tobacco smoke is a multicomponent mixture of chemical, organic, and inorganic compounds, as well as additive substances and radioactive materials. Many studies have proved the carcinogenicity of various of these compounds through the induction of DNA adducts, mutational potential, epigenetic changes, gene fusions, and chromosomal events. The tumor microenvironment plays an important role in malignant tumor formation and progression through the regulation of expression of key molecules which mediate the recruitment of immune cells to the tumor site and subsequently regulate tumor growth and metastasis. In this chapter, we discuss the effects of inhaled tobacco smoke in the tumor microenvironment of the respiratory tract. The mechanisms underlying these effects as well as their link with tumor progression are analyzed.

Tumor Microenvironment

Background and Objectives: The tumor microenvironment has been widely implicated in tumorigenesis because it harbors tumor cells that interact with surrounding cells through the circulatory and lymphatic systems to influence the development and progression of cancer. In addition, nonmalignant cells in the tumor microenvironment play critical roles in all the stages of carcinogenesis by stimulating and facilitating uncontrolled cell proliferation. Aim: This study aims to explore the concept of the tumor microenvironment by conducting a critical review of previous studies on the topic. Materials and Methods: This review relies on evidence presented in previous studies related to the topic. The articles included in this review were obtained from different medical and health databases. Results and Discussion: The tumor microenvironment has received significant attention in the cancer literature, with a particular focus on its role in tumor development and progression. Previous studies have identified various components of the tumor microenvironment that influence malignant behavior and progression. In addition to malignant cells, adipocytes, fibroblasts, tumor vasculature, lymphocytes, dendritic cells, and cancer-associated fibroblasts are present in the tumor microenvironment. Each of these cell types has unique immunological capabilities that determine whether the tumor will survive and affect neighboring cells. Conclusion: The tumor microenvironment harbors cancer stem cells and other molecules that contribute to tumor development and progression. Consequently, targeting and manipulating the cells and factors in the tumor microenvironment during cancer treatment can help control malignancies and achieve positive health outcomes.

Bcl11b prevents catastrophic autoimmunity by controlling multiple aspects of a regulatory T cell gene expression program

Foxp3 and its protein partners establish a regulatory T (T_reg) cell transcription profile and promote immunological tolerance. However, molecular features contributing to a T_reg-specific gene expression program are still incompletely understood. We find that the transcription factor Bcl11b is a prominent Foxp3 cofactor with multifaceted functions in T_reg biology. Optimal genomic recruitment of Foxp3 and Bcl11b is critically interdependent. Genome-wide occupancy studies coupled with gene expression profiling reveal that Bcl11b, in association with Foxp3, is primarily responsible in establishing a T_reg-specific gene activation program. Furthermore, Bcl11b restricts misdirected recruitment of Foxp3 to sites, which would otherwise result in an altered T_reg transcriptome profile. Consequently, T_reg-specific ablation of Bcl11b results in marked breakdown of immune tolerance, leading to aggressive systemic autoimmunity. Our study provides previously underappreciated mechanistic insights into molecular events contributing to basic aspects of T_reg function. Furthermore, it establishes a therapeutic target with potential implications in autoimmunity and cancer.

Tumor mechanisms of resistance to immune attack

The immune system plays a key role in the interactions between host and tumor. Immune selection pressure is a driving force behind the sculpting and evolution of malignant cancer cells to escape this immune attack. Several common tumor cell-based mechanisms of resistance to immune attack have been identified and can be broadly categorized into three main classes: loss of antigenicity, loss of immunogenicity, and creation of an immunosuppressive microenvironment. In this review, we will discuss in detail the relevant literature associated with each class of resistance and will describe the relevance of these mechanisms to human cancer patients. To conclude, we will outline the implications these mechanisms have for the treatment of cancer using currently available therapeutic approaches. Immunotherapy has been a successful addition to current treatment approaches, but many patients either do not respond or quickly become resistant. This reflects the ability of tumors to continue to adapt to immune selection pressure at all stages of development. Additional study of immune escape mechanisms and immunotherapy resistance mechanisms will be needed to inform future treatment approaches.

Neurological and Inflammatory Manifestations in Sjögren's Syndrome: The Role of the Kynurenine Metabolic Pathway

For decades, neurological, psychological, and cognitive alterations, as well as other glandular manifestations (EGM), have been described and are being considered to be part of Sjögren's syndrome (SS). Dry eye and dry mouth are major findings in SS. The lacrimal glands (LG), ocular surface (OS), and salivary glands (SG) are linked to the central nervous system (CNS) at the brainstem and hippocampus. Once compromised, these CNS sites may be responsible for autonomic and functional disturbances that are related to major and EGM in SS. Recent studies have confirmed that the kynurenine metabolic pathway (KP) can be stimulated by interferon-γ (IFN-γ) and other cytokines, activating indoleamine 2,3-dioxygenase (IDO) in SS. This pathway interferes with serotonergic and glutamatergic neurotransmission, mostly in the hippocampus and other structures of the CNS. Therefore, it is plausible that KP induces neurological manifestations and contributes to the discrepancy between symptoms and signs, including manifestations of hyperalgesia and depression in SS patients with weaker signs of sicca, for example. Observations from clinical studies in acquired immune deficiency syndrome (AIDS), graft-versus-host disease, and lupus, as well as from experimental studies, support this hypothesis. However, the obtained results for SS are controversial, as discussed in this study. Therapeutic strategies have been reexamined and new options designed and tested to regulate the KP. In the future, the confirmation and application of this concept may help to elucidate the mosaic of SS manifestations.

Effect of Stromal Cells in Tumor Microenvironment on Metastasis Initiation

The cellular environment where tumor cells reside is called the tumor microenvironment (TME), which consists of borders, blood vessels, lymph vessels, extracellular matrix (ECM), stromal cells, immune/inflammatory cells, secreted proteins, RNAs and small organelles. By dynamically interacting with tumor cells, stromal cells participate in all stages of tumor initiation, progression, metastasis, recurrence and drug response, and consequently, affect the fate of patients. During the processes of tumor evolution and metastasis initiation, stromal cells in TME also experience some changes and play roles in both the suppression and promotion of metastasis, while the overall function of stromal cells is beneficial for cancer cell survival and movement. In this review, we examine the effects of stromal cells in TME on metastasis initiation, including angiogenesis, epithelial-mesenchymal transition (EMT) and invasion. We also highlight functions of proteins, RNAs and small organelles secreted by stromal cells in their influences on multiple stages of tumor metastasis.

Native-mimicking in vitro microenvironment: an elusive and seductive future for tumor modeling and tissue engineering

Human connective tissues are complex physiological microenvironments favorable for optimal survival, function, growth, proliferation, differentiation, migration, and death of tissue cells. Mimicking native tissue microenvironment using various three-dimensional (3D) tissue culture systems in vitro has been explored for decades, with great advances being achieved recently at material, design and application levels. These achievements are based on improved understandings about the functionalities of various tissue cells, the biocompatibility and biodegradability of scaffolding materials, the biologically functional factors within native tissues, and the pathophysiological conditions of native tissue microenvironments. Here we discuss these continuously evolving physical aspects of tissue microenvironment important for human disease modeling, with a focus on tumors, as well as for tissue repair and regeneration. The combined information about human tissue spaces reflects the necessities of considerations when configuring spatial microenvironments in vitro with native fidelity to culture cells and regenerate tissues that are beyond the formats of 2D and 3D cultures. It is important to associate tissue-specific cells with specific tissues and microenvironments therein for a better understanding of human biology and disease conditions and for the development of novel approaches to treat human diseases.

Complex interplay between tumor microenvironment and cancer therapy

Tumor microenvironment (TME) is comprised of cellular and non-cellular components that exist within and around the tumor mass. The TME is highly dynamic and its importance in different stages of cancer progression has been well recognized. A growing body of evidence suggests that TME also plays pivotal roles in cancer treatment responses. TME is significantly remodeled upon cancer therapies, and such change either enhances the responses or induces drug resistance. Given the importance of TME in tumor progression and therapy resistance, strategies that remodel TME to improve therapeutic responses are under developing. In this review, we provide an overview of the essential components in TME and the remodeling of TME in response to anti-cancer treatments. We also summarize the strategies that aim to enhance therapeutic efficacy by modulating TME.

Regulatory T cells in retroviral infections

Tight regulation of immune responses is not only critical for preventing autoimmune diseases but also for preventing immunopathological damage during infections in which overactive immune responses may be more harmful for the host than the pathogen itself. Regulatory T cells (Tregs) play a critical role in this regulation, which was discovered using the Friend retrovirus (FV) mouse model. Subsequent FV studies revealed basic biological information about Tregs, including their suppressive activity on effector cells as well as the molecular mechanisms of virus-induced Treg expansion. Treg suppression not only limits immunopathology but also prevents complete elimination of pathogens contributing to chronic infections. Therefore, Tregs play a complex role in the pathogenesis of persistent retroviral infections. New therapeutic concepts to reactivate effector T-cell responses in chronic viral infections by manipulating Tregs also came from work with the FV model. This knowledge initiated many studies to characterize the role of Tregs in HIV pathogenesis in humans, where a complex picture is emerging. On one hand, Tregs suppress HIV-specific effector T-cell responses and are themselves targets of infection, but on the other hand, Tregs suppress HIV-induced immune hyperactivation and thus slow the infection of conventional CD4⁺ T cells and limit immunopathology. In this review, the basic findings from the FV mouse model are put into perspective with clinical and basic research from HIV studies. In addition, the few Treg studies performed in the simian immunodeficiency virus (SIV) monkey model will also be discussed. The review provides a comprehensive picture of the diverse role of Tregs in different retroviral infections and possible therapeutic approaches to treat retroviral chronicity and pathogenesis by manipulating Treg responses.

Regulatory T cells (Tregs) play a very complex role in retroviral infections, and the balance of beneficial versus detrimental effects from Tregs can change between the acute and chronic phase of infection. Therefore, the development of therapeutics to treat chronic retroviral infections via modulation of Tregs requires detailed information regarding both the positive and negative contributions of Tregs in a particular phase of a specific infection. Here, we review the molecular mechanisms that initiate and control Treg responses in retroviral infections as well as the target cells that are functionally manipulated by Tregs. Basic findings from the Friend retrovirus mouse model that initiated this area of research are put into perspective with clinical and basic research from HIV studies. The targeted manipulation of Treg responses holds a bright future for enhancing immune responses to infections, vaccine responses, and for cure or functional cure of chronic retroviral infections.

IL-4-Induced Gene 1: A Negative Immune Checkpoint Controlling B Cell Differentiation and Activation

Emerging data highlight the crucial role of enzymes involved in amino acid metabolism in immune cell biology. IL-4-induced gene-1 (IL4I1), a secreted l-phenylalanine oxidase expressed by APCs, has been detected in B cells, yet its immunoregulatory role has only been explored on T cells. In this study, we show that IL4I1 regulates multiple steps in B cell physiology. Indeed, IL4I1 knockout mice exhibit an accelerated B cell egress from the bone marrow, resulting in the accumulation of peripheral follicular B cells. They also present a higher serum level of natural Igs and self-reactive Abs. We also demonstrate that IL4I1 produced by B cells themselves controls the germinal center reaction, plasma cell differentiation, and specific Ab production in response to T dependent Ags, SRBC, and NP-KLH. In vitro, IL4I1-deficient B cells proliferate more efficiently than their wild-type counterparts in response to BCR cross-linking. Moreover, the absence of IL4I1 increases activation of the Syk-Akt-S6kinase signaling pathway and calcium mobilization, and inhibits SHP-1 activity upon BCR engagement, thus supporting that IL4I1 negatively controls BCR-dependent activation. Overall, our study reveals a new perspective on IL4I1 as a key regulator of B cell biology.

Emerging evidence for the role of differential tumor microenvironment in breast cancer racial disparity: a closer look at the surroundings

Although increased awareness leading to early detection and prevention, as well as advancements in treatment strategies, have resulted in superior clinical outcomes, African American women with breast cancer continue to have greater mortality rates, compared to Caucasian American counterparts. Moreover, African American women are more likely to have breast cancer at a younger age and be diagnosed with aggressive tumor sub-types. Such racial disparities can be attributed to socioeconomic differences, but it is increasingly being recognized that these disparities may indeed be due to certain genetic and other non-genetic biological differences. Tumor microenvironment, which provides a favorable niche for the growth of tumor cells, is comprised of several types of stromal cells and the various proteins secreted as a consequence of bi-directional tumor-stromal cross-talk. Emerging evidence suggests inherent biological differences in the tumor microenvironment of breast cancer patients from different racial backgrounds. Tumor microenvironment components, affected by the genetic make-up of the tumor cells as well as other non-tumor-associated factors, may also render patients more susceptible to the development of aggressive tumors and faster progression of disease resulting in early onset, thus adversely affecting patients' survival. This review provides an overview of breast cancer racial disparity and discusses the existence of race-associated differential tumor microenvironment and its underlying genetic and non-genetic causal factors. A better understanding of these aspects would help further research on effective cancer management and improved approaches for reducing the racial disparities gaps in breast cancer patients.

Transplant trials with Tregs: perils and promises

Modern immunosuppression regimens effectively control acute rejection and decrease graft loss in the first year after transplantation; however, these regimens do not have a durable effect on long-term graft survival owing to a combination of drug toxicities and the emergence of chronic alloimmune responses. Eliminating drugs and their toxicities while maintaining graft acceptance has been the primary aim of cellular therapies. Tregs suppress both autoimmune and alloimmune responses and are particularly effective in protecting allografts in experimental transplant models. Further, Treg-based therapies are selective, do not require harsh conditioning, and do not have a risk of graft-versus-host disease. Trial designs should consider the distinct immunological features of each transplanted organ, Treg preparations, dose, and frequency, and the ability to detect and quantify Treg effects in a given transplant environment. In this Review, we detail the ongoing clinical trials of Treg therapy in liver and kidney transplantation. Integration of Treg biology gleaned from preclinical models and experiences in human organ transplantation should allow for optimization of trial design that will determine the potential efficacy of a given therapy and provide guidelines for further therapeutic development.

CXCR5+CD8+ T cells infiltrate the colorectal tumors and nearby lymph nodes, and are associated with enhanced IgG response in B cells

Colorectal cancer is the third most prevalent cancer type worldwide and contributes to a significant percentage of cancer-related mortality. Recent studies have shown that the CXCR5⁺CD8⁺ T cells present more potent proinflammatory function than CXCR5^-CD8⁺ T cells in chronic virus infections and in follicular lymphoma, but the role of CXCR5⁺CD8⁺ T cells in colorectal cancer is yet unclear. In this study, we demonstrated that CXCR5⁺CD8⁺ T cells were very rare in peripheral blood mononuclear cells from healthy and colorectal cancer individuals, but were significantly enriched in resected tumors and tumor-associated lymph nodes. Compared to CXCR5^-CD8⁺ T cells, the CXCR5⁺CD8⁺ T cells demonstrated significantly higher Bcl-6 expression and lower Blimp1 expression, suggesting that CXCR5⁺CD8⁺ T cells might represent a memory CD8⁺ T cell subset. CXCR5⁺CD8⁺ T cells also enhanced the IgG expression by autologous B cells. Under ex vivo condition, the CXCR5⁺CD8⁺ T cells demonstrated lower degranulation, TNFα expression and IFNγ expression than CXCR5^-CD8⁺ T cells. However, after PMA + ionomycin stimulation, the degranulation and TNFα expression by CXCR5⁺CD8⁺ T cells were significantly elevated to a level comparable with CXCR5^-CD8⁺ T cells, whereas the IFNγ expression by PMA + ionomycin-stimulated CXCR5⁺CD8⁺ T cells were significantly higher than that by CXCR5^-CD8⁺ T cells. Following long-term TCR-stimulation, CXCR5⁺CD8⁺ T cells demonstrated significantly more potent proliferation capacity and higher IFNγ expression than CXCR5^-CD8⁺ T cells. TCR-stimulated CXCR5⁺CD8⁺ T cells also showed a gradual downregulation in CXCR5 expression. We further found that TCR-stimulated CXCR5⁺CD8⁺ T cells demonstrated higher granzyme B production and induced more specific lysis of autologous tumor cells than CXCR5^-CD8⁺ T cells. Together, these data demonstrate that CXCR5⁺CD8⁺ T cells represent a significant CD8⁺ T cell subset in colorectal tumors and have the potential to contribute to antitumor immunity, but their specific roles require further studies in vivo.

Analysis of Immune Response Markers in Jorge Lobo's Disease Lesions Suggests the Occurrence of Mixed T Helper Responses with the Dominance of Regulatory T Cell Activity

Jorge Lobo's disease (JLD) is a chronic infection that affects the skin and subcutaneous tissues. Its etiologic agent is the fungus Lacazia loboi. Lesions are classified as localized, multifocal, or disseminated, depending on their location. Early diagnosis and the surgical removal of lesions are the best therapeutic options currently available for JLD. The few studies that evaluate the immunological response of JLD patients show a predominance of Th2 response, as well as a high frequency of TGF-β and IL-10 positive cells in the lesions; however, the overall immunological status of the lesions in terms of their T cell phenotype has yet to be determined. Therefore, the objective of this study was to evaluate the pattern of Th1, Th2, Th17 and regulatory T cell (Treg) markers mRNA in JLD patients by means of real-time PCR. Biopsies of JLD lesions (N = 102) were classified according to their clinical and histopathological features and then analyzed using real-time PCR in order to determine the expression levels of TGF-β1, FoxP3, CTLA4, IKZF2, IL-10, T-bet, IFN-γ, GATA3, IL-4, IL-5, IL-13, IL-33, RORC, IL-17A, IL-17F, and IL-22 and to compare these levels to those of healthy control skin (N = 12). The results showed an increased expression of FoxP3, CTLA4, TGF-β1, IL-10, T-bet, IL-17F, and IL-17A in lesions, while GATA3 and IL-4 levels were found to be lower in diseased skin than in the control group. When the clinical forms were compared, TGF-β1 was found to be highly expressed in patients with a single localized lesion while IL-5 and IL-17A levels were higher in patients with multiple/disseminated lesions. These results demonstrate the occurrence of mixed T helper responses and suggest the dominance of regulatory T cell activity, which could inhibit Th-dependent protective responses to intracellular fungi such as L. loboi. Therefore, Tregs may play a key role in JLD pathogenesis.

Insulin-like growth factor-1 stimulates regulatory T cells and suppresses autoimmune disease

The recent precipitous rise in autoimmune diseases is placing an increasing clinical and economic burden on health systems worldwide. Current therapies are only moderately efficacious, often coupled with adverse side effects. Here, we show that recombinant human insulin-like growth factor-1 (rhIGF-1) stimulates proliferation of both human and mouse regulatory T (Treg) cells in vitro and when delivered systemically via continuous minipump, it halts autoimmune disease progression in mouse models of type 1 diabetes (STZ and NOD) and multiple sclerosis (EAE) in vivo. rhIGF-1 administration increased Treg cells in affected tissues, maintaining their suppressive properties. Genetically, ablation of the IGF-1 receptor specifically on Treg cell populations abrogated the beneficial effects of rhIGF-1 administration on the progression of multiple sclerotic symptoms in the EAE model, establishing a direct effect of IGF-1 on Treg cell proliferation. These results establish systemically delivered rhIGF-1 as a specific, effective stimulator of Treg cell action, underscoring the clinical feasibility of manipulating natural tolerance mechanisms to suppress autoimmune disease.

Partial dysfunction of Treg activation in sickle cell disease

Sickle cell disease (SCD) is a chronic inflammatory disease associated with multiple organ damage, chronic anemia, and infections. SCD patients have a high rate of alloimmunization against red blood cells (RBCs) following transfusion and may develop autoimmune diseases. Studies in mouse models have suggested that regulatory T cells (Treg) play a role in alloimmunization against RBC antigens. We characterized the phenotype and function of the Treg cell population in a homogeneous cohort of transfused SCD patients. We found that the distribution of Treg subpopulations differed significantly between SCD patients and healthy blood donors. SCD patients have a particular Treg phenotype, with strong CTLA-4 and CD39 expression and weak HLA-DR and CCR7 expression. Finally, we show that this particular phenotype is related to SCD rather than alloimmunization status. Indeed, we observed no difference in Treg phenotype or function in vitro using autologous feeder cells between strong and weak responders to alloimmunization.

CD4+ T helper cells use CD154-CD40 interactions to counteract T reg cell-mediated suppression of CD8+ T cell responses to influenza

CD40⁺ DCs interact with CD154⁺CD4⁺ T cells to abrogate T reg cell–mediated suppression of influenza-specific CD8⁺ T cells.

CD4⁺ T cells promote CD8⁺ T cell priming by licensing dendritic cells (DCs) via CD40–CD154 interactions. However, the initial requirement for CD40 signaling may be replaced by the direct activation of DCs by pathogen-derived signals. Nevertheless, CD40–CD154 interactions are often required for optimal CD8⁺ T cell responses to pathogens for unknown reasons. Here we show that CD40 signaling is required to prevent the premature contraction of the influenza-specific CD8⁺ T cell response. CD40 is required on DCs but not on B cells or T cells, whereas CD154 is required on CD4⁺ T cells but not CD8⁺ T cells, NKT cells, or DCs. Paradoxically, even though CD154-expressing CD4⁺ T cells are required for robust CD8⁺ T cell responses, primary CD8⁺ T cell responses are apparently normal in the absence of CD4⁺ T cells. We resolved this paradox by showing that the interaction of CD40-bearing DCs with CD154-expressing CD4⁺ T cells precludes regulatory T cell (T reg cell)–mediated suppression and prevents premature contraction of the influenza-specific CD8⁺ T cell response. Thus, CD4⁺ T helper cells are not required for robust CD8⁺ T cell responses to influenza when T reg cells are absent.

New effector functions and regulatory mechanisms of BCL6 in normal and malignant lymphocytes

The BCL6 oncogenic repressor is a master regulator of humoral immunity and B-cell lymphoma survival. Whereas much research has focused on its regulation and function in germinal center B-cells, its role in other mature lymphoid cell compartments is less clear. A novel role for BCL6 in follicular T helper cell development was recently uncovered. The latest discoveries reveal that BCL6 is also an important regulator of other specialized helper T-cell subsets within germinal centers, pre-germinal center events, and peripheral T-cell effector functions. Here, we review newly discovered roles for BCL6 in lymphocyte subsets residing within and outside of germinal centers, and discuss their implications with respect to the molecular mechanisms of BCL6 regulation and potential links to B and T-cell lymphomas.

Regulatory T cells use programmed death 1 ligands to directly suppress autoreactive B cells in vivo

The mechanisms by which regulatory T cells (T(regs)) suppress autoantibody production are unclear. Here we have addressed this question using transgenic mice expressing model antigens in the kidney. We report that T(regs) were essential and sufficient to suppress autoreactive B cells in an antigen-specific manner and to prevent them from producing autoantibodies. Most of this suppression was mediated through the inhibitory cell-surface-molecule programmed death-1 (PD-1). Suppression required PD-1 expression on autoreactive B cells and expression of the two PD-1 ligands on T(regs). PD-1 ligation inhibited activation of autoreactive B cells, suppressed their proliferation, and induced their apoptosis. Intermediate PD-1(+) cells, such as T helper cells, were dispensable for suppression. These findings demonstrate in vivo that T(regs) use PD-1 ligands to directly suppress autoreactive B cells, and they identify a previously undescribed peripheral B-cell tolerance mechanism against tissue autoantigens.

Taming lupus-a new understanding of pathogenesis is leading to clinical advances

Systemic lupus erythematosus (SLE) is an autoimmune disease that is characterized by the loss of tolerance to nuclear self antigens, the production of pathogenic autoantibodies and damage to multiple organ systems. Over the years, patients with SLE have been managed largely with empiric immunosuppressive therapies, which are associated with substantial toxicities and do not always provide adequate control of the disease. The development of targeted therapies that specifically address disease pathogenesis or progression has lagged, largely because of the complex and heterogeneous nature of the disease, as well as difficulties in designing uniform outcome measures for clinical trials. Recent advances that could improve the treatment of SLE include the identification of genetic variations that influence the risk of developing the disease, an enhanced understanding of innate and adaptive immune activation and regulation of tolerance, dissection of immune cell activation and inflammatory pathways and elucidation of mechanisms and markers of tissue damage. These discoveries, together with improvements in clinical trial design, form a platform from which to launch the development of a new generation of lupus therapies.

Highlights of the advances in basic immunology in 2011

In this review, we summarize the major fundamental advances in immunological research reported in 2011. The highlights focus on the improved understanding of key questions in basic immunology, including the initiation and activation of innate responses as well as mechanisms for the development and function of various T-cell subsets. The research includes the identification of novel cytosolic RNA and DNA sensors as well as the identification of the novel regulators of the Toll-like receptor (TLR) and retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) signaling pathway. Moreover, remarkable advances have been made in the developmental and functional properties of innate lymphoid cells (ILCs). Helper T cells and regulatory T (Treg) cells play indispensable roles in orchestrating adaptive immunity. There have been exciting discoveries regarding the regulatory mechanisms of the development of distinct T-cell subsets, particularly Th17 cells and Treg cells. The emerging roles of microRNAs (miRNAs) in T cell immunity are discussed, as is the recent identification of a novel T-cell subset referred to as follicular regulatory T (TFR) cells.

Does T Helper Differentiation Correlate with Resistance or Susceptibility to Infection with L. major? Some Insights From the Murine Model

The murine model of Leishmania major infection has been an invaluable tool in understanding T helper differentiation in vivo. The initial evidence for a role of distinct CD4⁺ T helper subsets in the outcome of infection was first obtained with this experimental model. The development of CD4⁺ Th1 cells was associated with resolution of the lesion, control of parasite replication, and resistance to re-infection in most of the mouse strains investigated (i.e., C57BL/6). In contrast, differentiation of CD4⁺ Th2 cells correlated with the development of unhealing lesions, and failure to control parasite load in a few strains (i.e., BALB/c). Since these first reports, an incredible amount of effort has been devoted to understanding the various parameters involved in the differentiation of these, and more recently discovered T helper subsets such as Th17 and T regulatory cells. The discovery of cross-talk between T helper subsets, as well as their plasticity force us to reevaluate the events driving a protective/deleterious T helper immune response following infection with L. major in mice. In this review, we describe the individual contributions of each of these CD4⁺ T helper subsets following L. major inoculation, emphasizing recent advances in the field, such as the impact of different substrains of L. major on the pathogenesis of disease.