STAT5 programs a distinct subset of GM-CSF-producing T helper cells that is essential for autoimmune neuroinflammation

Step-by-Step Immune Activation for Suicide Gene Therapy Reinforcement

Gene-directed enzyme prodrug gene therapy (GDEPT) theoretically represents a useful method to carry out chemotherapy for cancer with minimal side effects through the formation of a chemotherapeutic agent inside cancer cells. However, despite great efforts, promising preliminary results, and a long period of time (over 25 years) since the first mention of this method, GDEPT has not yet reached the clinic. There is a growing consensus that optimal cancer therapies should generate robust tumor-specific immune responses. The advent of checkpoint immunotherapy has yielded new highly promising avenues of study in cancer therapy. For such therapy, it seems reasonable to use combinations of different immunomodulators alongside traditional methods, such as chemotherapy and radiotherapy, as well as GDEPT. In this review, we focused on non-viral gene immunotherapy systems combining the intratumoral production of toxins diffused by GDEPT and immunomodulatory molecules. Special attention was paid to the applications and mechanisms of action of the granulocyte-macrophage colony-stimulating factor (GM–CSF), a cytokine that is widely used but shows contradictory effects. Another method to enhance the formation of stable immune responses in a tumor, the use of danger signals, is also discussed. The process of dying from GDEPT cancer cells initiates danger signaling by releasing damage-associated molecular patterns (DAMPs) that exert immature dendritic cells by increasing antigen uptake, maturation, and antigen presentation to cytotoxic T-lymphocytes. We hypothesized that the combined action of this danger signal and GM–CSF issued from the same dying cancer cell within a limited space would focus on a limited pool of immature dendritic cells, thus acting synergistically and enhancing their maturation and cytotoxic T-lymphocyte attraction potential. We also discuss the problem of enhancing the cancer specificity of the combined GDEPT–GM–CSF–danger signal system by means of artificial cancer specific promoters or a modified delivery system.

Deficiency of IL-27 Signaling Exacerbates Experimental Autoimmune Uveitis with Elevated Uveitogenic Th1 and Th17 Responses

Human uveitis is an autoimmune disease of the central nervous system that is characterized by ocular inflammation with the involvement of uveitogenic Th1 and Th17 responses. In experimental autoimmune uveitis (EAU), the animal model for human uveitis, both responses are proven to be critical in disease development. Therefore, targeting both Th1 and Th17 cells has therapeutic implication for disease resolution. IL-27 is a multifunctional cytokine that can either promote or inhibit T cell responses and is implicated in both autoimmune and infectious diseases. The aim of this study is to characterize the role of IL-27/IL-27R signaling in regulating uveitogenic Th1/Th17 responses in EAU. By immunizing IL-27Rα^-/- mice and their wild-type (WT) littermates for EAU, we demonstrated that IL-27 signaling deficiency exacerbated EAU with severe ocular inflammation and impairment of visual function. Furthermore, there was a significant increase in the eye-infiltrating Th1 and Th17 cells in IL-27Rα^-/- EAU mice compared to WT. Their retinal antigen-specific Th1 and Th17 responses were also significantly increased, as represented by the elevation of their signature cytokines, IFN-γ and IL-17A, respectively. We also observed the upregulation of another pathogenic cytokine, granulocyte-macrophage colony-stimulating factor (GM-CSF), from effector T cells in IL-27Rα^-/- EAU mice. Mechanistic studies confirmed that IL-27 inhibited GM-CSF production from Th17 cells. In addition, the induction of IL-10 producing type 1 regulatory T (Tr1) cells was impaired in IL-27Rα^-/- EAU mice. These results identified that IL-27 signaling plays a suppressive role in EAU by regulating multiple CD4⁺ cell subsets, including the effector Th1 and Th17 cells and the regulatory Tr1 cells. Our findings provide new insights for therapeutic potential in controlling uveitis by enhancing IL-27 signaling.

Gene Regulatory Network of Human GM-CSF-Secreting T Helper Cells

GM-CSF produced by autoreactive CD4-positive T helper cells is involved in the pathogenesis of autoimmune diseases, such as multiple sclerosis. However, the molecular regulators that establish and maintain the features of GM-CSF-positive CD4 T cells are unknown. In order to identify these regulators, we isolated human GM-CSF-producing CD4 T cells from human peripheral blood by using a cytokine capture assay. We compared these cells to the corresponding GM-CSF-negative fraction, and furthermore, we studied naïve CD4 T cells, memory CD4 T cells, and bulk CD4 T cells from the same individuals as additional control cell populations. As a result, we provide a rich resource of integrated chromatin accessibility (ATAC-seq) and transcriptome (RNA-seq) data from these primary human CD4 T cell subsets and we show that the identified signatures are associated with human autoimmune diseases, especially multiple sclerosis. By combining information about mRNA expression, DNA accessibility, and predicted transcription factor binding, we reconstructed directed gene regulatory networks connecting transcription factors to their targets, which comprise putative key regulators of human GM-CSF-positive CD4 T cells as well as memory CD4 T cells. Our results suggest potential therapeutic targets to be investigated in the future in human autoimmune disease.

Traffic-related PM2.5 and diverse constituents disturb the balance of Th17/Treg cells by STAT3/RORγt-STAT5/Foxp3 signaling pathway in a rat model of asthma

Water-soluble ions (WSI) and organic extract (OE) in traffic-related particulate matter with aerodynamic diameters ≤ 2.5 μm (TRPM2.5) are potential risk factors for asthma exacerbation. Although CD4+ T lymphocytes mediated immune response is involved in the pathogenesis of asthma, the effect of WSI-TRPM2.5 and OE-TRPM2.5 on the balance of Th17/Treg cells in asthma remains poorly understood. In this study, the ovalbumin (OVA)-sensitized rats were repeatedly exposure to TRPM2.5 (3 mg/kg·bw), WSI-TRPM2.5 (1.8 mg/kg·bw, 7.2 mg/kg·bw) and OE-TRPM2.5 (0.6 mg/kg·bw, 2.4 mg/kg·bw) every three days for five times. The inflammation response and hyperemia edema were observed in the lung and trachea tissues. DNA methylation levels of STAT3 and RORγt genes in rats with WSI-TRPM2.5 and OE-TRPM2.5 treatment were decreased. DNA methylation level in STAT5 gene tended to decrease, with no change observed on Foxp3 expression. WSI-TRPM2.5 and OE-TRPM2.5 enhanced the mRNA and protein expression of STAT3 and RORγt while inhibited the expression of STAT5 and Foxp3, which may contribute to the imbalance of Th17/Treg cells (P < 0.05). More importantly, recovered balance of Th17/Treg cell subsets, upregulated p-STAT5 and Foxp3 expression and reduced p-STAT3 and RORγt levels were observed after 5-Aza treatment. Our results demonstrate that the STAT3/RORγt-STAT5/Foxp3 signaling pathway is involved in asthma exacerbation induced by WSI-TRPM2.5 and OE-TRPM2.5 through disrupting the balance of Th17/Treg cells. The alteration of DNA methylation of STAT3, STAT5, and RORγt genes may be involved in asthma exacerbation as well.

Invasive mechanical ventilation and biomarkers as predictors of bronchopulmonary dysplasia in preterm infants

OBJECTIVES

To evaluate the impact of invasive mechanical ventilation associated with two serum inflammatory cytokines and clinical indicators, on the second day of life, as predictors of bronchopulmonary dysplasia in very low birth weight preterm infants. It was hypothesized that the use of invasive mechanical ventilation in the first hours of life is associated with biomarkers that may predict the chances of preterm infants to develop bronchopulmonary dysplasia.

METHODS

Prospective cohort of 40 preterm infants with gestational age <34 weeks and birth weight <1500 g. The following were analyzed: clinical variables; types of ventilator support used (there is a higher occurrence of bronchopulmonary dysplasia when oxygen supplementation is performed by long periods of invasive mechanical ventilation); hospitalization time; quantification of two cytokines (granulocyte and macrophage colony stimulating factor [GM-CSF] and eotaxin) in blood between 36 and 48 h of life. The preterm infants were divided in two groups: with and without bronchopulmonary dysplasia.

RESULTS

The GM-CSF levels presented a significantly higher value in the bronchopulmonary dysplasia group (p = 0.002), while eotaxin presented higher levels in the group without bronchopulmonary dysplasia (p = 0.02). The use of continuous invasive mechanical ventilation was associated with increased ratios between GM-CSF and eotaxin (100% sensitivity and 80% specificity; receiver operating characteristic area = 0.9013, CI = 0.7791-1.024, p < 0.0001).

CONCLUSIONS

The duration of invasive mechanical ventilation performed in the first 48 h of life in the very low birth weight infants is a significant clinical predictor of bronchopulmonary dysplasia. The use of continuous invasive mechanical ventilation was associated with increased ratios between GM-CSF and eotaxin, suggesting increased lung injury and consequent progression of the disease.

CD4+ T cells require Ikaros to inhibit their differentiation toward a pathogenic cell fate

The production of proinflammatory cytokines, particularly granulocyte-macrophage colony-stimulating factor (GM-CSF), by pathogenic CD4+ T cells is central for mediating tissue injury in inflammatory and autoimmune diseases. However, the factors regulating the T cell pathogenic gene expression program remain unclear. Here, we investigated how the Ikaros transcription factor regulates the global gene expression and chromatin accessibility changes in murine T cells during Th17 polarization and after activation via the T cell receptor (TCR) and CD28. We found that, in both conditions, Ikaros represses the expression of genes from the pathogenic signature, particularly Csf2, which encodes GM-CSF. We show that, in TCR/CD28-activated T cells, Ikaros binds a critical enhancer downstream of Csf2 and is required to regulate chromatin accessibility at multiple regions across this locus. Genome-wide Ikaros binding is associated with more compact chromatin, notably at multiple sites containing NFκB or STAT5 target motifs, and STAT5 or NFκB inhibition prevents GM-CSF production in Ikaros-deficient cells. Importantly, Ikaros also limits GM-CSF production in TCR/CD28-activated human T cells. Our data therefore highlight a critical conserved transcriptional mechanism that antagonizes GM-CSF expression in T cells.

The hedgehog pathway suppresses neuropathogenesis in CD4 T cell-driven inflammation

The concerted actions of the CNS and the immune system are essential to coordinating the outcome of neuroinflammatory responses. Yet, the precise mechanisms involved in this crosstalk and their contribution to the pathophysiology of neuroinflammatory diseases largely elude us. Here, we show that the CNS-endogenous hedgehog pathway, a signal triggered as part of the host response during the inflammatory phase of multiple sclerosis and experimental autoimmune encephalomyelitis, attenuates the pathogenicity of human and mouse effector CD4 T cells by regulating their production of inflammatory cytokines. Using a murine genetic model, in which the hedgehog signalling is compromised in CD4 T cells, we show that the hedgehog pathway acts on CD4 T cells to suppress the pathogenic hallmarks of autoimmune neuroinflammation, including demyelination and axonal damage, and thus mitigates the development of experimental autoimmune encephalomyelitis. Impairment of hedgehog signalling in CD4 T cells exacerbates brain-brainstem-cerebellum inflammation and leads to the development of atypical disease. Moreover, we present evidence that hedgehog signalling regulates the pathogenic profile of CD4 T cells by limiting their production of the inflammatory cytokines granulocyte-macrophage colony-stimulating factor and interferon-γ and by antagonizing their inflammatory program at the transcriptome level. Likewise, hedgehog signalling attenuates the inflammatory phenotype of human CD4 memory T cells. From a therapeutic point of view, our study underlines the potential of harnessing the hedgehog pathway to counteract ongoing excessive CNS inflammation, as systemic administration of a hedgehog agonist after disease onset effectively halts disease progression and significantly reduces neuroinflammation and the underlying neuropathology. We thus unveil a previously unrecognized role for the hedgehog pathway in regulating pathogenic inflammation within the CNS and propose to exploit its ability to modulate this neuroimmune network as a strategy to limit the progression of ongoing neuroinflammation.

STAT5 inhibitor attenuates atherosclerosis via inhibition of inflammation: the role of STAT5 in atherosclerosis

Atherosclerosis is a chronic inflammatory disease driven by lipids, which occurs preferentially in the branches or curved areas of the middle and large arteries, contributing to increased morbidity and mortality of cardiovascular disease. Recently, it has been reported that STAT5 and its regulated immune response are closely related to non-tumor diseases. However, the role of STAT5 in the development of atherosclerosis remains unknown. In this study, atherosclerosis was induced by high-fat diet (HFD) in ApoE^-/- mice, and STAT5-IN-1, a STAT5 inhibitor, was orally given. Macrophages stimulated by oxLDL were used as cell models in vitro. The effects of STAT5-IN-1 in ApoE^-/- mice induced by HFD were assessed, and the underlying mechanisms were investigated by siRNA-induced gene silencing. The results revealed that treatment with STAT5 inhibitor significantly attenuated atherosclerosis in ApoE^-/- mice induced by HFD via decreasing inflammation. Furthermore, it was demonstrated that inhibiting STAT5 could decrease oxLDL-induced inflammation. In summary, STAT5-IN-1 may be a potential drug for the treatment of atherosclerosis, and targeting STAT5 has the ability to be a potential therapeutic strategy for reducing atherosclerosis.

IL-23p19 and CD5 antigen-like form a possible novel heterodimeric cytokine and contribute to experimental autoimmune encephalomyelitis development

Among various cytokines, interleukin (IL)-12 family cytokines have very unique characteristics in that they are composed of two distinct subunits and these subunits are shared with each other. IL-23, one of the IL-12 family cytokines, consists of p19 and p40 subunits, is mainly produced by antigen-presenting cells, and plays a critical role in the expansion and maintenance of pathogenic helper CD4⁺ T (Th)17 cells. Since we initially found that p19 is secreted in the culture supernatant of activated CD4⁺ T cells, we have further investigated the role of p19. p19 was revealed to associate with CD5 antigen-like (CD5L), which is a repressor of Th17 pathogenicity and is highly expressed in non-pathogenic Th17 cells, to form a composite p19/CD5L. This p19/CD5L was shown to activate STAT5 and enhance the differentiation into granulocyte macrophage colony-stimulating factor (GM-CSF)-producing CD4⁺ T cells. Both CD4⁺ T cell-specific conditional p19-deficient mice and complete CD5L-deficient mice showed significantly alleviated experimental autoimmune encephalomyelitis (EAE) with reduced frequency of GM-CSF⁺CD4⁺ T cells. During the course of EAE, the serum level of p19/CD5L, but not CD5L, correlated highly with the clinical symptoms. Thus, the composite p19/CD5L is a possible novel heterodimeric cytokine that contributes to EAE development with GM-CSF up-regulation.

Interleukin-15 enhances proinflammatory T-cell responses in patients with MS and EAE

Objective

We posit that interleukin-15 (IL-15) is a relevant contributor to MS pathobiology as this cytokine is elevated in the CNS and periphery of patients with MS. We aim to investigate (1) the impact of IL-15 on T lymphocytes from patients with MS and (2) the in vivo role of IL-15 using the experimental autoimmune encephalomyelitis (EAE) mouse model.

Methods

We compared the impact of IL-15 on T lymphocytes obtained from untreated patients with MS (relapsing-remitting, secondary progressive, and primary progressive) to cells from age/sex-matched healthy controls (HCs) using multiparametric flow cytometry and in vitro assays. We tested the effects of peripheral IL-15 administration after EAE disease onset in C57BL/6 mice.

Results

IL-15 triggered STAT5 signaling in an elevated proportion of T cells from patients with MS compared with HCs. This cytokine also enhanced the production of key proinflammatory cytokines (interferon γ, granulocyte-macrophage colony-stimulating factor [GM-CSF], IL-17, and tumor necrosis factor) by T cells from both MS and controls, but these effects were more robust for the production of IL-17 and GM-CSF in T-cell subsets from patients with MS. At the peak of EAE disease, the proportion of CD4⁺ and CD8⁺ T cells expressing CD122⁺, the key signaling IL-15 receptor chain, was enriched in the CNS compared with the spleen. Finally, peripheral administration of IL-15 into EAE mice after disease onset significantly aggravated clinical scores and increased the number of inflammatory CNS-infiltrating T cells long term after stopping IL-15 administration.

Conclusions

Our results underscore that IL-15 contributes to the amplification of T-cell inflammatory properties after disease onset in both MS and EAE.

Imperfect storm: is interleukin-33 the Achilles heel of COVID-19?

The unique cytokine signature of COVID-19 might provide clues to disease mechanisms and possible future therapies. Here, we propose a pathogenic model in which the alarmin cytokine, interleukin (IL)-33, is a key player in driving all stages of COVID-19 disease (ie, asymptomatic, mild-moderate, severe-critical, and chronic-fibrotic). In susceptible individuals, IL-33 release by damaged lower respiratory cells might induce dysregulated GATA-binding factor 3-expressing regulatory T cells, thereby breaking immune tolerance and eliciting severe acute respiratory syndrome coronavirus 2-induced autoinflammatory lung disease. Such disease might be initially sustained by IL-33-differentiated type-2 innate lymphoid cells and locally expanded γδ T cells. In severe COVID-19 cases, the IL-33-ST2 axis might act to expand the number of pathogenic granulocyte-macrophage colony-stimulating factor-expressing T cells, dampen antiviral interferon responses, elicit hyperinflammation, and favour thromboses. In patients who survive severe COVID-19, IL-33 might drive pulmonary fibrosis by inducing myofibroblasts and epithelial-mesenchymal transition. We discuss the therapeutic implications of these hypothetical pathways, including use of therapies that target IL-33 (eg, anti-ST2), T helper 17-like γδ T cells, immune cell homing, and cytokine balance.

Cytokines and Transgenic Matrix in Autoimmune Diseases: Similarities and Differences

Autoimmune diseases are increasingly recognized as disease entities in which dysregulated cytokines contribute to tissue-specific inflammation. In organ-specific and multiorgan autoimmune diseases, the cytokine profiles show some similarities. Despite these similarities, the cytokines have different roles in the pathogenesis of different diseases. Altered levels or action of cytokines can result from changes in cell signaling. This article describes alterations in the JAK-STAT, TGF-β and NF-κB signaling pathways, which are involved in the pathogenesis of multiple sclerosis and systemic lupus erythematosus. There is a special focus on T cells in preclinical models and in patients afflicted with these chronic inflammatory diseases.

Cytokine-regulated Th17 plasticity in human health and diseases

Upon activation, naïve CD4⁺ T helper (Th) cells differentiate into distinct Th effector cell lineages depending on the local cytokine environment. However, these polarized Th cells can also adapt their function and phenotype depending on the changing cytokine environment, demonstrating functional plasticity. Here, Th17 cells, which play a critical role in host protection from extracellular pathogens and in autoimmune disorders, are of particular interest. While being able to shift phenotype within their lineage, Th17 cells can also acquire characteristics of Th1, Th2, T follicular helper (Tfh) or regulatory T cells. Th17 cell identity is determined by a spectrum of extracellular signals, including cytokines, which are critical orchestrators of cellular immune responses. Cytokine induces changes in epigenetic, transcriptional, translational and metabolomic parameters. How these signals are integrated to determine Th17 plasticity is not well defined, yet this is a crucial point of investigation as it represents a potential target to treat autoimmune and inflammatory diseases. The goal of this review was to discuss how cytokines regulate intracellular networks, focusing on the regulation of lineage-specific transcription factors, chromatin remodelling and metabolism, to control human Th17 cell plasticity. We discuss the importance of Th17 plasticity in autoimmunity and cancer and present current strategies and challenges in targeting pathogenic Th17 cells with cytokine-based approaches, considering human genetic variants associated with altered Th17 differentiation. Finally, we discuss how modulating Th17 plasticity rather than targeting the Th17 lineage as a whole might preserve its essential immune function while purging its adverse effects.

GM-CSF: A Promising Target in Inflammation and Autoimmunity

The cytokine, granulocyte macrophage-colony stimulating factor (GM-CSF), was firstly identified as being able to induce in vitro the proliferation and differentiation of bone marrow progenitors into granulocytes and macrophages. Much preclinical data have indicated that GM-CSF has a wide range of functions across different tissues in its action on myeloid cells, and GM-CSF deletion/depletion approaches indicate its potential as an important therapeutic target in several inflammatory and autoimmune disorders, for example, rheumatoid arthritis. In this review, we discuss briefly the biology of GM-CSF, raise some current issues and questions pertaining to this biology, summarize the results from preclinical models of a range of inflammatory and autoimmune disorders and list the latest clinical trials evaluating GM-CSF blockade in such disorders.

Modulation of PKM activity affects the differentiation of TH17 cells

Small molecules that promote the metabolic activity of the pyruvate kinase isoform PKM2, such as TEPP-46 and DASA-58, limit tumorigenesis and inflammation. To understand how these compounds alter T cell function, we assessed their therapeutic activity in a mouse model of T cell-mediated autoimmunity that mimics multiple sclerosis (MS). TH17 cells are believed to orchestrate MS pathology, in part, through the production of two proinflammatory cytokines: interleukin-17 (IL-17) and GM-CSF. We found that both TEPP-46 and DASA-58 suppressed the development of IL-17-producing TH17 cells but increased the generation of those producing GM-CSF. This switch redirected disease pathology from the spinal cord to the brain. In addition, we found that activation of PKM2 interfered with TGF-β1 signaling, which is necessary for the development of TH17 and regulatory T cells. Collectively, our data clarify the therapeutic potential of PKM2 activators in MS-like disease and how these agents alter T cell function.

A distinct GM-CSF+ T helper cell subset requires T-bet to adopt a TH1 phenotype and promote neuroinflammation

Elevation of granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing T helper (T_H) cells has been associated with several autoimmune diseases, suggesting a potential role in the pathogenesis of autoimmunity. However, the identity of GM-CSF-producing T_H cells has not been closely examined. Using single-cell RNA sequencing and high-dimensional single-cell mass cytometry, we identified eight populations of antigen-experienced CD45RA^-CD4⁺ T cells in blood of healthy individuals including a population of GM-CSF-producing cells, known as T_HGM, that lacked expression of signature transcription factors and cytokines of established T_H lineages. Using GM-CSF-reporter/fate reporter mice, we show that T_HGM cells are present in the periphery and central nervous system in a mouse model of experimental autoimmune encephalomyelitis. In addition to GM-CSF, human and mouse T_HGM cells also expressed IL-2, tumor necrosis factor (TNF), IL-3, and CCL20. T_HGM cells maintained their phenotype through several cycles of activation but up-regulated expression of T-bet and interferon-γ (IFN-γ) upon exposure to IL-12 in vitro and in the central nervous system of mice with autoimmune neuroinflammation. Although T-bet was not required for the development of T_HGM cells, it was essential for their encephalitogenicity. These findings demonstrate that T_HGM cells constitute a distinct population of T_H cells with lineage characteristics that are poised to adopt a T_H1 phenotype and promote neuroinflammation.

Th17/Treg imbalance in COPD development: suppressors of cytokine signaling and signal transducers and activators of transcription proteins

Th17/Treg imbalance contributes to chronic obstructive pulmonary disease (COPD) development and progression. However, intracellular signaling by suppressor of cytokine signaling (SOCS) 1 and SOCS3 and the proteins signal transducer and activator of transcription (STAT) 3 and STAT5 that orchestrate these imbalances are currently poorly understood. Thus, these proteins were investigated in C57BL/6 mice after exposure to cigarette smoke (CS) for 3 and 6 months. The expression of interleukin was measured by ELISA and the density of positive cells in peribronchovascular areas was quantified by immunohistochemistry. We showed that exposure to CS in the 3rd month first induced decreases in the numbers of STAT5+ and pSTAT5+ cells and the expression levels of TGF-β and IL-10. The increases in the numbers of STAT3+ and pSTAT3+ cells and IL-17 expression occurred later (6th month). These findings corroborate the increases in the number of SOCS1+ cells in both the 3rd and 6th months, with concomitant decreases in SOCS3+ cells at the same time points. Our results demonstrated that beginning with the initiation of COPD development, there was a downregulation of the anti-inflammatory response mediated by SOCS and STAT proteins. These results highlight the importance of intracellular signaling in Th17/Treg imbalance and the identification of possible targets for future therapeutic approaches.

Constitutive Expression of CCL22 Is Mediated by T Cell-Derived GM-CSF

CCL22 is a key mediator of leukocyte trafficking in inflammatory immune responses, allergy, and cancer. It acts by attracting regulatory T cells and Th2 cells via their receptor CCR type 4 (CCR4). Beyond its role in inflammation, CCL22 is constitutively expressed at high levels in lymphoid organs during homeostasis, where it controls immunity by recruiting regulatory T cells to dendritic cells (DCs). In this study, we aimed to identify the mechanisms responsible for constitutive CCL22 expression. We confirmed that CD11c⁺ DCs are the exclusive producers of CCL22 in secondary lymphatic organs during homeostasis. We show that in vitro both murine splenocytes and human PBMCs secrete CCL22 spontaneously without any further stimulation. Interestingly, isolated DCs alone, however, are unable to produce CCL22, but instead require T cell help. In vitro, only the coculture of DCs with T cells or their supernatants resulted in CCL22 secretion, and we identified T cell-derived GM-CSF as the major inducer of DC-derived CCL22 expression. In vivo, Rag1 ^-/- mice, which lack functional T cells, have low CCL22 levels in lymphoid organs, and this can be restored by adoptive transfer of wild-type T cells or administration of GM-CSF. Taken together, we uncover T cell-derived GM-CSF as a key inducer of the chemokine CCL22 and thus, to our knowledge, identify a novel role for this cytokine as a central regulator of immunity in lymphatic organs. This knowledge could contribute to the development of new therapeutic interventions in cancer and autoimmunity.

Increased IL-2 and Reduced TGF-β Upon T-Cell Stimulation are Associated with GM-CSF Upregulation in Multiple Immune Cell Types in Multiple Sclerosis

Granulocyte macrophage colony stimulating factor (GM-CSF) is a pro-inflammatory cytokine produced by immune cells. Recent evidence suggests that GM-CSF plays an important role in multiple sclerosis (MS) pathogenesis. We investigated the expression and regulation of GM-CSF in different immune cells in MS. We also investigated the differentiation and frequency of GM-CSF-producing Th cells that do not co-express interferon (IFN)-γ or interleukin-17 (IL-17) (Th-GM cells) in MS. We found a significant increase in the percentage of GM-CSF-expressing Th cells, Th1 cells, Th-GM cells, cytotoxic T (Tc) cells, monocytes, natural killer (NK) cells, and B cells in PBMC from MS patients stimulated with T cell stimuli. Stimulated PBMC culture supernatants from MS patients contained significantly higher levels of IL-2, IL-12, IL-1β, and GM-CSF and significantly lower levels of transforming growth factor (TGF-)β. Blocking IL-2 reduced the frequency of Th-GM cells in PBMC from MS patients. The frequency of Th-GM cells differentiated in vitro from naïve CD4⁺ T cells was significantly higher in MS patients and was further increased in MS with IL-2 stimulation. These findings suggest that all main immune cell subsets produce more GM-CSF in MS after in vitro stimulation, which is associated with defective TGF-β and increased IL-2 and IL-12 production. Th-GM cells are increased in MS. GM-CSF may be a potential therapeutic target in MS.

Pathogenic T cell cytokines in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system that is believed to have an autoimmune etiology. As MS is the most common nontraumatic disease that causes disability in young adults, extensive research has been devoted to identifying therapeutic targets. In this review, we discuss the current understanding derived from studies of patients with MS and animal models of how specific cytokines produced by autoreactive CD4 T cells contribute to the pathogenesis of MS. Defining the roles of these cytokines will lead to a better understanding of the potential of cytokine-based therapies for patients with MS.

GM-CSF in inflammation

GM-CSF is a potential therapeutic target in inflammation and autoimmunity. This study reviews the literature on the biology of GM-CSF, in particular that describing the research leading to clinical trials targeting GM-CSF and its receptor in numerous inflammatory/autoimmune conditions, such as rheumatoid arthritis.

Granulocyte–macrophage colony-stimulating factor (GM-CSF) has many more functions than its original in vitro identification as an inducer of granulocyte and macrophage development from progenitor cells. Key features of GM-CSF biology need to be defined better, such as the responding and producing cell types, its links with other mediators, its prosurvival versus activation/differentiation functions, and when it is relevant in pathology. Significant preclinical data have emerged from GM-CSF deletion/depletion approaches indicating that GM-CSF is a potential target in many inflammatory/autoimmune conditions. Clinical trials targeting GM-CSF or its receptor have shown encouraging efficacy and safety profiles, particularly in rheumatoid arthritis. This review provides an update on the above topics and current issues/questions surrounding GM-CSF biology.

Dimethyl fumarate suppresses granulocyte macrophage colony-stimulating factor-producing Th1 cells in CNS neuroinflammation

Objective

To study the immunomodulatory effect of dimethyl fumarate (DF) on granulocyte macrophage colony-stimulating factor (GM-CSF) production in CD4⁺ T cells in experimental autoimmune encephalomyelitis (EAE) and human peripheral blood mononuclear cells (PBMCs).

Methods

We collected splenocytes and CD4⁺ T cells from C57BL/6 wild-type and interferon (IFN)-γ–deficient mice. For human PBMCs, venous blood was collected from healthy donors, and PBMCs were collected using the Percoll gradient method. Cells were cultured with anti-CD3/28 in the presence/absence of DF for 3 to 5 days. Cells were stained and analyzed by flow cytometry. Cytokines were measured by ELISA in cell supernatants. For in vivo experiments, EAE was induced by myelin oligodendrocyte glycoprotein_35–55 and mice were treated with oral DF or vehicle daily.

Results

DF acts directly on CD4⁺ T cells and suppresses GM-CSF–producing Th1 not Th17 or single GM-CSF⁺ T cells in EAE. In addition, GM-CSF suppression depends on the IFN-γ pathway. We also show that DF specifically suppresses Th1 and GM-CSF–producing Th1 cells in PBMCs from healthy donors.

Conclusions

We suggest that DF exclusively suppresses GM-CSF–producing Th1 cells in both animal and human CD4⁺ T cells through an IFN-γ–dependent pathway. These findings indicate that DF has a better therapeutic effect on patients with Th1-dominant immunophenotype. However, future longitudinal study to validate this finding in MS is needed.

The Role of Granulocyte-Macrophage Colony-Stimulating Factor in Murine Models of Multiple Sclerosis

Multiple sclerosis (MS) is an immune-mediated disease that predominantly impacts the central nervous system (CNS). Animal models have been used to elucidate the underpinnings of MS pathology. One of the most well-studied models of MS is experimental autoimmune encephalomyelitis (EAE). This model was utilized to demonstrate that the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) plays a critical and non-redundant role in mediating EAE pathology, making it an ideal therapeutic target. In this review, we will first explore the role that GM-CSF plays in maintaining homeostasis. This is important to consider, because any therapeutics that target GM-CSF could potentially alter these regulatory processes. We will then focus on current findings related to the function of GM-CSF signaling in EAE pathology, including the cell types that produce and respond to GM-CSF and the role of GM-CSF in both acute and chronic EAE. We will then assess the role of GM-CSF in alternative models of MS and comment on how this informs the understanding of GM-CSF signaling in the various aspects of MS immunopathology. Finally, we will examine what is currently known about GM-CSF signaling in MS, and how this has promoted clinical trials that directly target GM-CSF.

Liver fibrosis and CD206+ macrophage accumulation are suppressed by anti-GM-CSF therapy

Background & Aims

Chronic liver inflammation leads to fibrosis and cirrhosis and is associated with an accumulation of intrahepatic TNFα-secreting CD206⁺ macrophages, which may participate in maintaining chronic liver disease in a GM-CSF-dependent manner. We aimed to elucidate the exact role of GM-CSF in the development and progression of chronic liver disease.

Methods

Liver immunohistochemistry and serum quantification were performed in patients with viral and non-viral-related liver disease to compare CD206⁺ monocyte/macrophages, fibrosis and GM-CSF. This was followed by functional validations in vitro and in vivo in humanised mice.

Results

Using multiplex immunofluorescence and histo-cytometry, we show that highly fibrotic livers had a greater density of CD206⁺ macrophages that produced more TNFα and GM-CSF in the non-tumour liver regions of patients with hepatocellular carcinoma (n = 47), independent of aetiology. In addition, the absolute number of CD206⁺ macrophages strongly correlated with the absolute number of GM-CSF-producing macrophages. In non-HCC chronic HCV⁺ patients (n = 40), circulating GM-CSF levels were also increased in proportion to the degree of liver fibrosis and serum viral titres. We then demonstrated in vitro that monocytes converted to TNFα-producing CD206⁺ macrophage-like cells in response to bacterial products (lipopolysaccharide) in a GM-CSF-dependent manner, confirming the in vivo normalisation of serum GM-CSF concentration following oral antibiotic treatment observed in HBV-infected humanised mice. Finally, anti-GM-CSF neutralising antibody treatment reduced intrahepatic CD206⁺ macrophage accumulation and abolished liver fibrosis in HBV-infected humanised mice.

Conclusions

While the direct involvement of CD206⁺ macrophages in liver fibrosis remains to be demonstrated, these findings show that GM-CSF may play a central role in liver fibrosis and could guide the development of anti-GM-CSF antibody-based therapy for the management of patients with chronic liver disease.

Lay summary

Liver fibrosis is a major driver of liver disease progression. Herein, we have shown that granulocyte-macrophage colony-stimulating factor (GM-CSF) plays an important role in the development of liver fibrosis. Our findings support the use of anti-GM-CSF neutralising antibodies for the management of patients with chronic liver disease resulting from both viral and non-viral causes.

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GM-CSF and TNFα producing CD206⁺ macrophages accumulate in human fibrotic liver

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Serum GM-CSF is increased in HCV⁺ patients with higher liver fibrosis

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GM-CSF drives monocyte to CD206⁺ macrophage conversion

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Anti-GM-CSF therapy suppresses liver fibrosis and CD206⁺ macrophage accumulation

ECM1 is an essential factor for the determination of M1 macrophage polarization in IBD in response to LPS stimulation

Inflammatory bowel disease (IBD) comprises chronic relapsing disorders of the gastrointestinal tract characterized pathologically by intestinal inflammation and epithelial injury. Here, we uncover a function of extracellular matrix protein 1 (ECM1) in promoting the pathogenesis of human and mouse IBD. ECM1 was highly expressed in macrophages, particularly tissue-infiltrated macrophages under inflammatory conditions, and ECM1 expression was significantly induced during IBD progression. The macrophage-specific knockout of ECM1 resulted in increased arginase 1 (ARG1) expression and impaired polarization into the M1 macrophage phenotype after lipopolysaccharide (LPS) treatment. A mechanistic study showed that ECM1 can regulate M1 macrophage polarization through the granulocyte-macrophage colony-stimulating factor/STAT5 signaling pathway. Pathological changes in mice with dextran sodium sulfate-induced IBD were alleviated by the specific knockout of the ECM1 gene in macrophages. Taken together, our findings show that ECM1 has an important function in promoting M1 macrophage polarization, which is critical for controlling inflammation and tissue repair in the intestine.

Rebound of disease activity after fingolimod withdrawal: Immunological and gene expression profiling

Discontinuation of disease-modifying therapy with fingolimod can lead to severe Multiple Sclerosis (MS) rebound activity; however, this phenomenon remains mechanistically incompletely understood, and the short-term impact of a therapy switch on inflammatory gene expression in T lymphocytes is unknown. We present the clinico-radiological and immunological description of a case of rebound activity after fingolimod discontinuation and switching to rituximab treatment in a relapsing-remitting MS patient. After severe rebound, a reduction in the expression of inflammatory cytokines and transcription factors was rapidly observed after administration of methylprednisolone and rituximab. Rituximab led to an effective suppression of inflammatory activity, and at least in this specific case it represented a valid switching approach after fingolimod discontinuation.

T Cell Antifungal Immunity and the Role of C-Type Lectin Receptors

Fungi can cause disease in humans, from mucocutaneous to life-threatening systemic infections. Initiation of antifungal immunity involves fungal recognition by pattern recognition receptors such as C-type lectin receptors (CLRs). These germline-encoded receptors trigger a multitude of innate responses including phagocytosis, fungal killing, and antigen presentation which can also shape the development of adaptive immunity. Recently, studies have shed light on how CLRs directly or indirectly modulate lymphocyte function. Moreover, CLR-mediated recognition of commensal fungi maintains homeostasis and prevents invasion from opportunistic commensals. We present an overview of current knowledge of antifungal T cell immune responses, with emphasis on the role of C-type lectins, and discuss how these receptors modulate these responses at different levels.

CLRs are essential pattern recognition receptors involved in fungal recognition and initiation of protective antifungal immunity.

CLRs promote the differentiation of mammalian T helper cell subsets essential for the control of systemic (Th1) and mucosal (Th17) fungal infections.

CLRs are involved in antigen presentation, the expression of co-stimulatory molecules, and cytokine secretion; therefore, they can regulate lymphocyte function and adaptive immune responses at different levels.

Fungal morphological changes, such as the transition from yeast to hyphae in Candida albicans during tissue invasion, affects recognition by CLRs and impacts on adaptive immune responses.

CLRs recognize the fungal component of the microbiome that can influence T cell responses during infection at intestinal and peripheral sites.

Targeting STAT3 and STAT5 in Tumor-Associated Immune Cells to Improve Immunotherapy

Oncogene-induced STAT3-activation is central to tumor progression by promoting cancer cell expression of pro-angiogenic and immunosuppressive factors. STAT3 is also activated in infiltrating immune cells including tumor-associated macrophages (TAM) amplifying immune suppression. Consequently, STAT3 is considered as a target for cancer therapy. However, its interplay with other STAT-family members or transcription factors such as NF-κB has to be considered in light of their concerted regulation of immune-related genes. Here, we discuss new attempts at re-educating immune suppressive tumor-associated macrophages towards a CD8 T cell supporting profile, with an emphasis on the role of STAT transcription factors on TAM functional programs. Recent clinical trials using JAK/STAT inhibitors highlighted the negative effects of these molecules on the maintenance and function of effector/memory T cells. Concerted regulation of STAT3 and STAT5 activation in CD8 T effector and memory cells has been shown to impact their tumor-specific responses including intra-tumor accumulation, long-term survival, cytotoxic activity and resistance toward tumor-derived immune suppression. Interestingly, as an escape mechanism, melanoma cells were reported to impede STAT5 nuclear translocation in both CD8 T cells and NK cells. Ours and others results will be discussed in the perspective of new developments in engineered T cell-based adoptive therapies to treat cancer patients.

STAT3 and STAT5 Signaling Thresholds Determine Distinct Regulation for Innate Receptor-Induced Inflammatory Cytokines, and STAT3/STAT5 Disease Variants Modulate These Outcomes

Genetic variants in the STAT3/STAT5A/STAT5B region are associated with immune-mediated diseases, including inflammatory bowel disease (IBD). However, how STAT3 and STAT5 regulate the critical balance between pro- and anti-inflammatory cytokines and how common disease-associated genetic variants (e.g., rs12942547) in the region modulate this balance are incompletely understood. We found that upon pattern-recognition receptor (PRR) stimulation of human monocyte-derived macrophages (MDMs), decreasing STAT3, STAT5a, and STAT5b expression led to a progressive decrease in anti-inflammatory cytokines, whereas proinflammatory cytokines initially decreased but then increased when STAT3 or STAT5 expression fell below a critical threshold. Mechanisms regulating STAT3- and STAT5-dependent inflammatory cytokine outcomes included negative feedback from autocrine/paracrine IL-10, TGF-β, IL-4, IL-13, IL-22, and TSLP secretion and SOCS1/SOCS2/SOCS3 induction. MDMs from rs12942547 AA disease-risk carriers demonstrated increased STAT3, STAT5a, and STAT5b expression and increased PRR-induced STAT3 and STAT5 phosphorylation relative to GG MDMs. Both pro- and anti-inflammatory cytokine secretion was decreased in MDMs from GG carriers, as STAT3, STAT5a, and STAT5b expression was above the threshold for reciprocal regulation of these cytokines. Taken together, we identify that the threshold of STAT3, STAT5a, and STAT5b expression determines if PRR-induced proinflammatory cytokines are increased or decreased, define mechanisms for this reciprocal regulation, and elucidate consequences for disease variants in the STAT3/STAT5A/STAT5B region, indicating that considering signaling thresholds and targeting specific cell types might be beneficial when evaluating therapeutic interventions in this pathway.

STAT3 and STAT5 Targeting for Simultaneous Management of Melanoma and Autoimmune Diseases

Melanoma is a skin cancer which can become metastatic, drug-refractory, and lethal if managed late or inappropriately. An increasing number of melanoma patients exhibits autoimmune diseases, either as pre-existing conditions or as sequelae of immune-based anti-melanoma therapies, which complicate patient management and raise the need for more personalized treatments. STAT3 and/or STAT5 cascades are commonly activated during melanoma progression and mediate the metastatic effects of key oncogenic factors. Deactivation of these cascades enhances antitumor-immune responses, is efficient against metastatic melanoma in the preclinical setting and emerges as a promising targeting strategy, especially for patients resistant to immunotherapies. In the light of the recent realization that cancer and autoimmune diseases share common mechanisms of immune dysregulation, we suggest that the systemic delivery of STAT3 or STAT5 inhibitors could simultaneously target both, melanoma and associated autoimmune diseases, thereby decreasing the overall disease burden and improving quality of life of this patient subpopulation. Herein, we review the recent advances of STAT3 and STAT5 targeting in melanoma, explore which autoimmune diseases are causatively linked to STAT3 and/or STAT5 signaling, and propose that these patients may particularly benefit from treatment with STAT3/STAT5 inhibitors.

GM-CSF and CXCR4 define a T helper cell signature in multiple sclerosis

Cytokine dysregulation is a central driver of chronic inflammatory diseases such as multiple sclerosis (MS). Here we sought to determine the characteristic cellular and cytokine polarization profile in patients with relapsing-remitting multiple sclerosis (RRMS) by high-dimensional single-cell mass cytometry (CyTOF). Using a combination of neural network-based representation learning algorithms, we identified an expanded T helper cell subset in MS patients, characterized by the expression of GM-CSF and the C-X-C chemokine receptor type 4. This cellular signature, which includes expression of very late antigen 4 (VLA4) in peripheral blood, was also enriched in the central nervous system of RRMS patients. In independent validation cohorts, we confirmed that this cell population is increased in MS patients compared to other inflammatory and non-inflammatory conditions. Lastly, we also found the population to be reduced under effective disease-modifying therapy, suggesting that the identified T cell profile represents a specific therapeutic target in MS.

Single-cell Analysis of CAR-T Cell Activation Reveals A Mixed TH1/TH2 Response Independent of Differentiation

The activation mechanism of chimeric antigen receptor (CAR)-engineered T cells may differ substantially from T cells carrying native T cell receptor, but this difference remains poorly understood. We present the first comprehensive portrait of single-cell level transcriptional and cytokine signatures of anti-CD19/4-1BB/CD28/CD3ζ CAR-T cells upon antigen-specific stimulation. Both CD4⁺ helper T (T_H) cells and CD8⁺ cytotoxic CAR-T cells are equally effective in directly killing target tumor cells and their cytotoxic activity is associated with the elevation of a range of T_H1 and T_H2 signature cytokines, e.g., interferon γ, tumor necrotic factor α, interleukin 5 (IL5), and IL13, as confirmed by the expression of master transcription factor genes TBX21 and GATA3. However, rather than conforming to stringent T_H1 or T_H2 subtypes, single-cell analysis reveals that the predominant response is a highly mixed T_H1/T_H2 function in the same cell. The regulatory T cell activity, although observed in a small fraction of activated cells, emerges from this hybrid T_H1/T_H2 population. Granulocyte-macrophage colony stimulating factor (GM-CSF) is produced from the majority of cells regardless of the polarization states, further contrasting CAR-T to classic T cells. Surprisingly, the cytokine response is minimally associated with differentiation status, although all major differentiation subsets such as naïve, central memory, effector memory, and effector are detected. All these suggest that the activation of CAR-engineered T cells is a canonical process that leads to a highly mixed response combining both type 1 and type 2 cytokines together with GM-CSF, supporting the notion that polyfunctional CAR-T cells correlate with objective response of patients in clinical trials. This work provides new insights into the mechanism of CAR activation and implies the necessity for cellular function assays to characterize the quality of CAR-T infusion products and monitor therapeutic responses in patients.

Roles of GM-CSF in the Pathogenesis of Autoimmune Diseases: An Update

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was first described as a growth factor that induces the differentiation and proliferation of myeloid progenitors in the bone marrow. GM-CSF also has an important cytokine effect in chronic inflammatory diseases by stimulating the activation and migration of myeloid cells to inflammation sites, promoting survival of target cells and stimulating the renewal of effector granulocytes and macrophages. Because of these pro-cellular effects, an imbalance in GM-CSF production/signaling may lead to harmful inflammatory conditions. In this context, GM-CSF has a pathogenic role in autoimmune diseases that are dependent on cellular immune responses such as multiple sclerosis (MS) and rheumatoid arthritis (RA). Conversely, a protective role has also been described in other autoimmune diseases where humoral responses are detrimental such as myasthenia gravis (MG), Hashimoto's thyroiditis (HT), inflammatory bowel disease (IBD), and systemic lupus erythematosus (SLE). In this review, we aimed for a comprehensive analysis of literature data on the multiple roles of GM-CSF in autoimmue diseases and possible therapeutic strategies that target GM-CSF production.

Generation of IL-3-Secreting CD4+ T Cells by Microbial Challenge at Skin and Mucosal Barriers

During Ag priming, naive CD4⁺ T cells differentiate into subsets with distinct patterns of cytokine expression that dictate to a major extent their functional roles in immune responses. We identified a subset of CD4⁺ T cells defined by secretion of IL-3 that was induced by Ag stimulation under conditions different from those associated with previously defined functional subsets. Using mouse models of bacterial and viral infections, we showed that IL-3–secreting CD4⁺ T cells were generated by infection at the skin and mucosa but not by infections introduced directly into the blood. Most IL-3–producing T cells coexpressed GM-CSF and other cytokines that define multifunctionality. Generation of IL-3–secreting T cells in vitro was dependent on IL-1 family cytokines and was inhibited by cytokines that induce canonical Th1 or Th2 cells. Our results identify IL-3–secreting CD4⁺ T cells as a potential functional subset that arises during priming of naive T cells in specific tissue locations.

Interleukin-1β-induced IRAK1 ubiquitination is required for TH-GM-CSF cell differentiation in T cell-mediated inflammation

Accumulating evidence suggests granulocyte macrophage-colony stimulating factor (GM-CSF) can function as an inflammatory mediator, but whether GM-CSF-producing CD4⁺ T cells (T_H-GM-CSF) are a distinct T helper cell subset is lacking. Herein we demonstrate that interleukin (IL)-1β exclusively drives differentiation of naïve CD4⁺ T cells into T_H-GM-CSF cells via inducing ubiquitination of IL-1 receptor-associated kinase 1 (IRAK1) and subsequent activation of the transcription factor NF-kappaB (NF-κB), independent of RAR-related orphan receptor gamma (RORγt) required for T_H17 differentiation. In vivo, T_H-GM-CSF cells are present in murine Citrobacter Rodentium infections and mediate colitis following adoptive transfer of CD4⁺ T cells into Rag1^-/- mice via GM-CSF-induced macrophage activation. The T_H-GM-CSF cell phenotype is stable and distinct from the T_H17 genetic program, but IL-1β can convert pre-formed T_H17 cells into T_H-GM-CSF cells, thereby accounting for previously reported associations between IL-17 and GM-CSF. Together, our results newly identify IL-1β/NF-κB-dependent T_H-GM-CSF cells as a unique T helper cell subset and highlight the importance of CD4⁺ T cell-derived GM-CSF induced macrophage activation as a previously undescribed T cell effector mechanism.

ST2/MyD88 Deficiency Protects Mice against Acute Graft-versus-Host Disease and Spares Regulatory T Cells

Acute graft-versus-host disease (aGVHD) hinders the efficacy of allogeneic hematopoietic cell transplantation (HCT). Plasma levels of soluble membrane-bound ST2 (ST2) are elevated in human and murine aGVHD and correlated to type 1 T cells response. ST2 signals through the adapter protein MyD88. The role of MyD88 in T cells during aGVHD has yet to be elucidated. We found that knocking out MyD88 in the donor T cells protected against aGVHD independent of IL-1R and TLR4 signaling in two murine HCT models. This protection was entirely driven by MyD88^-/- CD4 T cells. Transplanting donor MyD88^-/- conventional T cells (Tcons) with wild-type (WT) or MyD88^-/- regulatory T cells (Tregs) lowered aGVHD severity and mortality. Transcriptome analysis of sorted MyD88^-/- CD4 T cells from the intestine 10 d post-HCT showed lower levels of Il1rl1 (gene of ST2), Ifng, Csf2, Stat5, Batf, and Jak2 Transplanting donor ST2^-/- Tcons with WT or ST2^-/- Tregs showed a similar phenotype with what we observed when using donor MyD88^-/- Tcons. Decreased ST2 was confirmed at the protein level with less secretion of soluble ST2 and more expression of ST2 compared with WT T cells. Our data suggest that Treg suppression from lack of MyD88 signaling in donor Tcons during alloreactivity uses the ST2 but not the IL-1R or TLR4 pathways, and ST2 represents a potential aGVHD therapeutic target sparing Tregs.

Association of synovial tissue polyfunctional T-cells with DAPSA in psoriatic arthritis

OBJECTIVE

This study examines polyfunctional T-cells in psoriatic arthritis (PsA) synovial tissue and their associations with clinical disease and implications for therapy.

METHODS

PsA synovial tissue was enzymatically/mechanically digested to generate synovial tissue single cell suspensions. Frequencies of polyfunctional CD4, CD8, T-helper 1 (Th1), Th17 and exTh17 cells, using CD161 as a marker of Th17 plasticity, were determined by flow cytometry in matched PsA synovial tissue and peripheral blood. Synovial T-cell polyfunctionality was assessed in relation to Disease Activity in PSoriatic Arthritis (DAPSA) and in synovial cell suspensions cultured with a current mode of treatment, phosphodiesterase 4 (PDE4) inhibitor.

RESULTS

PsA synovial tissue infiltrating CD4+ T-cells expressed higher levels of interleukin (IL)-17A, interferon gamma (IFN-γ), GM-CSF and CD161, with parallel enrichment of Th1, Th17 and exTh17 T-helper subsets (all p<0.05). Interestingly, a significant proportion of synovial T-cell subsets were triple-positive for GM-CSF, tumour necrosis factor (-TNF), -IL-17 or IFN-γ compared with matched blood (all p<0.05). Importantly, frequencies of polyfunctional T-cells correlated with DAPSA: Th1-GM-CSF+/TNF+/IFN-γ+ (r=0.7, p<0.01), Th17-GM-CSF+/TNF+/IL-17+ (r=0.6, p<0.057) and exTh17-GM-CSF+/TNF+/IFN-γ+ (r=0.7, p=0.0096), with no associations observed for single cytokine-producing T-cells. Following ex vivo culture of PsA synovial tissue cell suspensions, polyfunctional GM-CSF+TNFα+IL-17A+ or/IFN-γ+-producing T-cells (p<0.05), but not single cytokine-producing T-cells, were inhibited with a PDE4 inhibitor.

CONCLUSION

These data demonstrate enrichment of polyfunctional T-cells in PsA synovial tissue which were strongly associated with DAPSA and ex vivo therapeutic response.

Innate Immune Modulation by GM-CSF and IL-3 in Health and Disease

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and inteleukin-3 (IL-3) have long been known as mediators of emergency myelopoiesis, but recent evidence has highlighted their critical role in modulating innate immune effector functions in mice and humans. This new wealth of knowledge has uncovered novel aspects of the pathogenesis of a range of disorders, including infectious, neoplastic, autoimmune, allergic and cardiovascular diseases. Consequently, GM-CSF and IL-3 are now being investigated as therapeutic targets for some of these disorders, and some phase I/II clinical trials are already showing promising results. There is also pre-clinical and clinical evidence that GM-CSF can be an effective immunostimulatory agent when being combined with anti-cytotoxic T lymphocyte-associated protein 4 (anti-CTLA-4) in patients with metastatic melanoma as well as in novel cancer immunotherapy approaches. Finally, GM-CSF and to a lesser extent IL-3 play a critical role in experimental models of trained immunity by acting not only on bone marrow precursors but also directly on mature myeloid cells. Altogether, characterizing GM-CSF and IL-3 as central mediators of innate immune activation is poised to open new therapeutic avenues for several immune-mediated disorders and define their potential in the context of immunotherapies.

Self-reactive CD4+ IL-3+ T cells amplify autoimmune inflammation in myocarditis by inciting monocyte chemotaxis

Acquisition of self-reactive effector CD4⁺ T cells is a major component of the autoimmune response that can occur during myocarditis, an inflammatory form of cardiomyopathy. Although the processes by which self-reactive T cells gain effector function have received considerable attention, how these T cells contribute to effector organ inflammation and damage is less clear. Here, we identified an IL-3-dependent amplification loop that exacerbates autoimmune inflammation. In experimental myocarditis, we show that effector organ-accumulating autoreactive IL-3⁺ CD4⁺ T cells stimulate IL-3R⁺ tissue macrophages to produce monocyte-attracting chemokines. The newly recruited monocytes differentiate into antigen-presenting cells that stimulate local IL-3⁺ CD4⁺ T cell proliferation, thereby amplifying organ inflammation. Consequently, Il3 ^-/- mice resist developing robust autoimmune inflammation and myocardial dysfunction, whereas therapeutic IL-3 targeting ameliorates disease. This study defines a mechanism that orchestrates inflammation in myocarditis, describes a previously unknown function for IL-3, and identifies IL-3 as a potential therapeutic target in patients with myocarditis.

Granulocyte-Macrophage Colony-Stimulating Factor as a Therapeutic Target in Multiple Sclerosis

Multiple sclerosis is an inflammatory neurodegenerative disease of the central nervous system (CNS) and the most frequent cause of non-traumatic disability in adults in the Western world. Currently, several drugs have been approved for the treatment of multiple sclerosis. While the newer drugs are more effective, they have less favourable safety profiles. Thus, there is a need to identify new targets for effective and safe therapies, particularly in patients with progressive disease for whom no treatments are available. One such target is granulocyte-macrophage colony-stimulating factor (GM-CSF) or its receptor. In this article we review data on the potential role of GM-CSF and GM-CSF inhibition in MS. We discuss the expression and function of GM-CSF and its receptor in the CNS, as well as data from animal studies and clinical trials in MS.

Experimental Autoimmune Encephalomyelitis (EAE) as Animal Models of Multiple Sclerosis (MS)

Multiple sclerosis (MS) is a multifocal demyelinating disease of the central nervous system (CNS) leading to the progressive destruction of the myelin sheath surrounding axons. It can present with variable clinical and pathological manifestations, which might reflect the involvement of distinct pathogenic processes. Although the mechanisms leading to the development of the disease are not fully understood, numerous evidences indicate that MS is an autoimmune disease, the initiation and progression of which are dependent on an autoimmune response against myelin antigens. In addition, genetic susceptibility and environmental triggers likely contribute to the initiation of the disease. At this time, there is no cure for MS, but several disease-modifying therapies (DMTs) are available to control and slow down disease progression. A good number of these DMTs were identified and tested using animal models of MS referred to as experimental autoimmune encephalomyelitis (EAE). In this review, we will recapitulate the characteristics of EAE models and discuss how they help shed light on MS pathogenesis and help test new treatments for MS patients.

Regulation of Lymphatic GM-CSF Expression by the E3 Ubiquitin Ligase Cbl-b

Genome-wide association studies as well as lymphatic expression analyses have linked both Cbl-b and GM-CSF to human multiple sclerosis as well as other autoimmune diseases. Both Cbl-b and GM-CSF have been shown to play a prominent role in the development of murine encephalomyelitis; however, no functional connection between the two has yet been established. In this study, we show that Cblb knockout mice demonstrated significantly exacerbated severity of experimental autoimmune encephalomyelitis (EAE), augmented T cell infiltration into the central nervous system (CNS) and strongly increased production of GM-CSF in T cells in vitro and in vivo.GM-CSF neutralization demonstrated that the increased susceptibility of Cblb^−/− mice to EAE was dependent on GM-CSF. Mechanistically, p50 binding to the GM-CSF promoter and the IL-3/GM-CSF enhancer element “CNSa” was strongly increased in nuclear extracts from Cbl-b-deficient T cells. This study suggests that Cbl-b limits autoimmunity by preventing the pathogenic effects of GM-CSF overproduction in T cells.

Prophylactic treatment against GM-CSF, but not IL-17, abolishes relapses in a chronic murine model of multiple sclerosis

The pathogenic role of IL-17 and GM-CSF has been unravelled in experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS). However, in most models, EAE is characterised by a monophasic attack which is not representative of the relapsing nature nor the chronicity displayed in MS. Here, we used proteolipid protein peptide (PLP_139-151 ) to trigger EAE-relapses (EAE-II) in SJL mice that had recovered from a primary-EAE episode (EAE-I). This procedure resulted in severe and irreversible disease that, unlike EAE-I, was not abolished by anti-IL-17-mAb. In contrast, prophylactic anti-GM-CSF-mAb treatment prevented EAE-I and -II. Strikingly, the expression of T-cell transcription factors and cytokines/chemokines in mice treated with anti-GM-CSF during both EAE episodes was silenced. Anti-GM-CSF-mAb treatment administered only during EAE-II did not completely prevent relapses but mice ultimately reached full recovery. Anti-GM-CSF treatment also strongly impaired and ultimately resolved monophasic MOG_35-55 -induced EAE in C57Bl/6 mice. In such protected mice, anti-GM-CSF treatment also prevented a further relapse induced by MOG-revaccination. These results underscore the critical role of GM-CSF on pro-inflammatory mediator production. Furthermore, we observed a strong preventive and curative effect of anti-GM-CSF neutralisation in two EAE models, relapsing and chronic. Altogether these findings are relevant for further MS research.

In Vitro Differentiation of Mouse Granulocyte-macrophage-colony-stimulating Factor (GM-CSF)-producing T Helper (THGM) Cells

The granulocyte-macrophage-colony-stimulating factor (GM-CSF)-producing T helper (THGM) cell is a newly identified T helper cell subset that predominantly secretes GM-CSF without producing interferon (IFN)γ or interleukin (IL)-17 and is found to play an essential role in the autoimmune neuroinflammation. A method of isolation of naive CD4+ T cells from a single-cell suspension of splenocytes and THGM cell generation from naive CD4+ T cells would be a useful technique in the study of T cell-mediated immunity and autoimmune diseases. Here we describe a method that differentiates mouse naive CD4+ T cells into THGM cells promoted by IL-7. The outcome of the differentiation was assessed by the analysis of the cytokines expression using different techniques, including intracellular cytokine staining combined with flow cytometry, a quantitative real-time polymerase chain reaction (PCR), and enzyme-linked immunosorbent assays (ELISA). Using the THGM differentiation protocol as described here, about 55% of the cells expressed GM-CSF with a minimal expression of IFNα or IL-17. The predominant expression of GM-CSF by THGM cells was further confirmed by the analysis of the expression of GM-CSF, IFNα, and IL-17 at both mRNA and protein levels. Thus, this method can be used to differentiate naive CD4+ T cells to THGM cells in vitro, which will be useful in the study of THGM cell biology.

The Common Cytokine Receptor γ Chain Family of Cytokines

Interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21 form a family of cytokines based on their sharing the common cytokine receptor γ chain (γc), which was originally discovered as the third receptor component of the IL-2 receptor, IL-2Rγ. The IL2RG gene is located on the X chromosome and is mutated in humans with X-linked severe combined immunodeficiency (XSCID). The breadth of the defects in XSCID could not be explained solely by defects in IL-2 signaling, and it is now clear that γc is a shared receptor component of the six cytokines noted above, making XSCID a disease of defective cytokine signaling. Janus kinase (JAK)3 associates with γc, and JAK3-deficient SCID phenocopies XSCID, findings that served to stimulate the development of JAK3 inhibitors as immunosuppressants. γc family cytokines collectively control broad aspects of lymphocyte development, growth, differentiation, and survival, and these cytokines are clinically important, related to allergic and autoimmune diseases and cancer as well as immunodeficiency. In this review, we discuss the actions of these cytokines, their critical biological roles and signaling pathways, focusing mainly on JAK/STAT (signal transducers and activators of transcription) signaling, and how this information is now being used in clinical therapeutic efforts.