New complexities in helper T cell fate determination and the implications for autoimmune diseases

Interleukin-17 in Chronic Inflammatory Neurological Diseases

A critical role for IL-17, a cytokine produced by T helper 17 (Th17) cells, has been indicated in the pathogenesis of chronic inflammatory and autoimmune diseases. A positive effect of blockade of IL-17 secreted by autoreactive T cells has been shown in various inflammatory diseases. Several cytokines, whose production is affected by environmental factors, control Th17 differentiation and its maintenance in tissues during chronic inflammation. The roles of IL-17 in the pathogenesis of chronic neuroinflammatory conditions, multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE), Alzheimer's disease, and ischemic brain injury are reviewed here. The role of environmental stimuli in Th17 differentiation is also summarized, highlighting the role of viral infection in the regulation of pathogenic T helper cells in EAE.

COVID-19: The Inflammation Link and the Role of Nutrition in Potential Mitigation

The novel coronavirus disease (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has engulfed the world, affecting more than 180 countries. As a result, there has been considerable economic distress globally and a significant loss of life. Sadly, the vulnerable and immunocompromised in our societies seem to be more susceptible to severe COVID-19 complications. Global public health bodies and governments have ignited strategies and issued advisories on various handwashing and hygiene guidelines, social distancing strategies, and, in the most extreme cases, some countries have adopted "stay in place" or lockdown protocols to prevent COVID-19 spread. Notably, there are several significant risk factors for severe COVID-19 infection. These include the presence of poor nutritional status and pre-existing noncommunicable diseases (NCDs) such as diabetes mellitus, chronic lung diseases, cardiovascular diseases (CVD), obesity, and various other diseases that render the patient immunocompromised. These diseases are characterized by systemic inflammation, which may be a common feature of these NCDs, affecting patient outcomes against COVID-19. In this review, we discuss some of the anti-inflammatory therapies that are currently under investigation intended to dampen the cytokine storm of severe COVID-19 infections. Furthermore, nutritional status and the role of diet and lifestyle is considered, as it is known to affect patient outcomes in other severe infections and may play a role in COVID-19 infection. This review speculates the importance of nutrition as a mitigation strategy to support immune function amid the COVID-19 pandemic, identifying food groups and key nutrients of importance that may affect the outcomes of respiratory infections.

Pathological significance and regulatory mechanism of lymphotoxin β receptor overexpression in T cells of patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a typical autoimmune disease. Lymphotoxin β receptor (LTβR) signaling plays an important role in autoimmune inflammations. LTβR-Ig fusion protein, LTβR blocking agent, has been used to treat SLE, while its mechanism remains to be fully elucidated. In this study, to investigate the expression of LTβR in the T cells of SLE patients and its roles in the pathogenesis of SLE, we isolated the peripheral blood T cells of SLE patients and normal controls to detect expression of LTβR by flow cytometry and RNA assay. T cells were also stimulated with LIGHT, a ligand of LTβR, and then detected for their LTβR expressions and apoptosis by flow cytometry. Also, their expressions of inflammatory factors and receptors were determined by RNA assay. The results showed that LTβR positive cells were 22.75%±6.98% in CD3⁺ cells of SLE patients, while there were almost no LTβR positive cells in CD3⁺ cells of normal persons. Moreover, LTβR expression was remarkably higher in CD3, CD4 and CD8 positive T cells of active SLE patients than non/low active patients (all P<0.05), and positively correlated with increased Ig level, decreased complement level and renal damage. Moreover, the stimulation of SLE T cells with LIGHT promoted higher expression of LTβR, IL-23R and IL-17A, and apoptosis of T cells. In conclusion, we demonstrated a high expression of LTβR in the T cells of SLE patients which may be associated with pathogenesis of SLE.

Are Microglial Cells the Regulators of Lymphocyte Responses in the CNS?

The infiltration of immune cells in the central nervous system is a common hallmark in different neuroinflammatory conditions. Accumulating evidence indicates that resident glial cells can establish a cross-talk with infiltrated immune cells, including T-cells, regulating their recruitment, activation and function within the CNS. Although the healthy CNS has been thought to be devoid of professional dendritic cells (DCs), numerous studies have reported the presence of a population of DCs in specific locations such as the meninges, choroid plexuses and the perivascular space. Moreover, the infiltration of DC precursors during neuroinflammatory situations has been proposed, suggesting a putative role of these cells in the regulation of lymphocyte activity within the CNS. On the other hand, under specific circumstances, microglial cells are able to acquire a phenotype of DC expressing a wide range of molecules that equip these cells with all the necessary machinery for communication with T-cells. In this review, we summarize the current knowledge on the expression of molecules involved in the cross-talk with T-cells in both microglial cells and DCs and discuss the potential contribution of each of these cell populations on the control of lymphocyte function within the CNS.

Human interleukin-27: wide individual variation in plasma levels and complex inter-relationships with interleukin-17A

Although it is widely believed that interleukin (IL)-27 is anti-inflammatory, its role in controlling human immune responses is not fully established. In particular, its interactions with T helper type 17 (Th)17 cytokines are unclear. Our aims were to establish the relationships between IL-27 and proinflammatory cytokines, including IL-17A, in human sera and cultures of peripheral blood mononuclear cells. Plasma IL-27 levels in 879 healthy humans from 163 families varied widely, but with relatively low heritability (19%). Despite IL-27 including a subunit encoded by Epstein-Barr virus-induced gene 3 (EBI3), there was no correlation of levels with serological evidence of infection with the virus. Although IL-27 has been reported to inhibit IL-17A production, we demonstrated a strong positive correlation in sera, but lower correlations of IL-27 with other proinflammatory cytokines. We verified that IL-27 inhibited IL-17A production by human peripheral blood T cells in vitro, but not that it stimulated IL-10 secretion. Importantly, addition of IL-17A decreased IL-27 production by stimulated T cells but had the opposite effect on resting T cells. Together, these data suggest a model whereby IL-27 and IL-17A exerts complex reciprocal effects to boost inflammatory responses, but restrain resting cells to prevent inappropriate activation.

Regulation of adipose tissue T cell subsets by Stat3 is crucial for diet-induced obesity and insulin resistance

Dysregulated inflammation in adipose tissue, marked by increased proinflammatory T-cell accumulation and reduced regulatory T cells (Tregs), contributes to obesity-associated insulin resistance. The molecular mechanisms underlying T-cell-mediated inflammation in adipose tissue remain largely unknown, however. Here we show a crucial role for signal transducer and activator of transcription 3 (Stat3) in T cells in skewing adaptive immunity in visceral adipose tissue (VAT), thereby contributing to diet-induced obesity (DIO) and insulin resistance. Stat3 activity is elevated in obese VAT and in VAT-resident T cells. Functional ablation of Stat3 in T cells reduces DIO, improves insulin sensitivity and glucose tolerance, and suppresses VAT inflammation. Importantly, Stat3 ablation reverses the high Th1/Treg ratio in VAT of DIO mice that is likely secondary to elevated IL-6 production, leading in turn to suppression of Tregs. In addition, Stat3 in T cells in DIO mice affects adipose tissue macrophage accumulation and M2 phenotype. Our study identifies Stat3 in VAT-resident T cells as an important mediator and direct target for regulating adipose tissue inflammation, DIO, and its associated metabolic dysfunctions.

IL-23/IL-17A axis correlates with the nitric oxide pathway in inflammatory bowel disease: immunomodulatory effect of retinoic acid

Inflammatory bowel diseases (IBDs) are chronic inflammatory diseases of the gastrointestinal tract, which are clinically present as 1 of the 2 disorders, Crohn's disease (CD) or ulcerative colitis (UC) (Rogler 2004). The immune dysregulation in the intestine plays a critical role in the pathogenesis of IBD, involving a wide range of molecules, including cytokines. The aim of this work was to study the involvement of T-helper 17 (Th17) subset in the bowel disease pathogenesis by the nitric oxide (NO) pathway in Algerian patients with IBD. We investigated the correlation between the proinflammatory cytokines [(interleukin (IL)-17, IL-23, and IL-6] and NO production in 2 groups of patients. We analyzed the expression of messenger RNAs (mRNAs) encoding Th17 cytokines, cytokine receptors, and NO synthase 2 (NOS2) in plasma of the patients. In the same way, the expression of p-signal transducer and activator of transcription 3 (STAT3) and NOS2 was measured by immunofluorescence and immunohistochemistry. We also studied NO modulation by proinflammatory cytokines (IL-17A, IL-6, tumor necrosis factor α, or IL-1β) in the presence or absence of all-trans retinoic acid (At RA) in peripheral blood mononuclear cells (PBMCs), monocytes, and in colonic mucosa cultures. Analysis of cytokines, cytokine receptors, and NOS2 transcripts revealed that the levels of mRNA transcripts of the indicated genes are elevated in all IBD groups. Our study shows a significant positive correlation between the NO and IL-17A, IL-23, and IL-6 levels in plasma of the patients with IBD. Interestingly, the correlation is significantly higher in patients with active CD. Our study shows that both p-STAT3 and inducible NOS expression was upregulated in PBMCs and colonic mucosa, especially in patients with active CD. At RA downregulates NO production in the presence of proinflammatory cytokines for the 2 groups of patients. Collectively, our study indicates that the IL-23/IL-17A axis plays a pivotal role in IBD pathogenesis through the NO pathway.

The efficacy and safety of Jitongning Capsule () in patients with ankylosing spondylitis

OBJECTIVE

To confirm the efficacy and safety of Jitongning Capsule in the treatment of ankylosing spondylitis (AS).

METHODS

A total of 120 AS patients with early-intermediate were randomly and equally assigned to Jitongning Capsule group and sulfasalazine group. Jitongning Capsule was orally taken 4.5 g per day and sulfasalazine was orally taken 2 g daily for 12 months. The primary endpoint was the proportion of patients achieving the Assessment in Ankylosing Spondylitis 20 (ASAS 20), secondary end points included Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), Bath Ankylosing Spondylitis Metrology Index (BASMI), patient's global assessment by VAS rating, spinal pain, general pain and night pain, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and interleukin-4 (IL-4) in the peripheral blood mononuclear cells (PBMC) of AS patients were measured.

RESULTS

A total of 111 patients completed the study. There were 58 patients in Jitongning group and 53 patients in sulfasalazine group. Both drugs showed mild and occasional side effects. After treated by Jitongning Capsule and sulfasalazine, the proportion of ASAS20 responders at 12 month was 72.41% (42/58) and 67.92% (36/53) respectively. Both Jitongning Capsule and sulfasalazine treatment induced significant decrease in the proportion of CD4(+)T cell and CD8(+)T cell expressing TNF-α and IFN-γ at 12-month of treatment compared with baseline values (P<0.05).

CONCLUSION

Jitongning Capsule are effective in a setting close to real-life medical care with a sustained improvement in signs and symptoms of AS, and reduce cytokine levels in PBMC. It showed comparable effects to sulfasalazine.

Isothiocyanates inhibit psoriasis-related proinflammatory factors in human skin

OBJECTIVE

4-Methylthiobutylisothiocyanate (MTBI), the main rocket (Eruca sativa) seed isothiocyanate (ITC), and its oxidized form, sulforaphane (SFN), were assessed for their potential effects on psoriasis-related factors.

METHODS

MTBI and SFN were evaluated for their effect on mRNA expression and cytokine secretion in vitro in human monocytes and macrophage-like cells and ex vivo in topically treated inflamed human skin. In addition, they were assayed in vivo for morphological changes in topically treated psoriasiform human skin in severe-combined immunodeficient (SCID) mice.

RESULTS

MTBI and SFN contributed to the prevention of inflammation development and reduced ongoing inflammation by downregulating lipopolysaccharide (LPS)-induced mRNA expression of the psoriasis-related cytokines, interleukin (IL)-12/23p40 (25-58 %), tumor necrosis factor (TNF)-α (15-37 %) and IL-6 (25-71 %), in human macrophage-like cells. In monocytes, they tended to act additively on cytokine mRNA and reduced IL-12/23p40 (51 %) secretion. In an ex-vivo inflamed human skin organ culture, MTBI (1 μg/ml) reduced the secretion of IL-1 (39 %) and IL-6 (32 %). Moreover, 2/8 and 3/8 of the MTBI- and SFN-treated psoriasiform SCID mice, respectively, recovered partially or entirely from the psoriasiform process.

CONCLUSIONS

Results from these models indicate the potential of rocket seed ITCs as biological agents in the therapy of psoriasis and inflammation-related skin diseases.

A murine autoimmune model of rheumatoid arthritis and systemic lupus erythematosus associated with deregulated production of IL-17 and IL-21

T-helper cell 17 (Th17) cells play an important role in the pathogenesis of many autoimmune disorders including Rheumatoid Arthritis (RA) and Systemic Lupus Erythematosus (SLE). In this chapter we describe a murine model where deregulated production of IL-17 and IL-21 can lead to either lupus-like disease or RA-like symptoms depending on the genetic background. We delineate the key techniques that can be used to dissect the mechanisms responsible for the pathogenesis of these diseases at both a cellular and molecular level including in vitro Th17 cell differentiation, chromatin immunoprecipitation assays, and retroviral transduction experiments. We also describe the methodologies that can be utilized to monitor the classic clinical findings of RA and SLE in murine models. Given the broad involvement of deregulated production of IL-17 and IL-21 in autoimmunity, many of these techniques could also be valuable for the investigation of these pathways in murine models of other autoimmune diseases.

Increase in Th17 and T-reg lymphocytes and decrease of IL22 correlate with the recovery phase of acute EAE in rat

Experimental autoimmune encephalomyelitis (EAE), a well-established model of multiple sclerosis, is characterised by microglial activation and lymphocyte infiltration. Induction of EAE in Lewis rats produces an acute monophasic disease characterised by a single peak of disability followed by a spontaneous and complete recovery and a subsequent tolerance to further immunizations. In the current study we have performed a detailed analysis of the dynamics of different lymphocyte populations and cytokine profile along the induction, peak, recovery and post-recovery phases in this paradigm. MBP-injected rats were sacrificed attending exclusively to their clinical score, and the different populations of T-lymphocytes as well as the dynamics of different pro- and anti-inflammatory cytokines were analysed in the spinal cord by flow cytometry, immunohistochemistry and ELISA. Our results revealed that, during the induction and peak phases, in parallel to an increase in symptomatology, the number of CD3+ and CD4+ cells increased progressively, showing a Th1 phenotype, but unexpectedly during recovery, although clinical signs progressively decreased, the number and proportion of CD3+ and CD4+ populations remained unaltered. Interestingly, during this recovery phase, we observed a marked decrease of Th1 and an important increase in Th17 and T-reg cells. Moreover, our results indicate a specific cytokine expression profile along the EAE course characterized by no changes of IL10 and IL17 levels, decrease of IL21 on the peak, and high IL22 levels during the induction and peak phases that markedly decrease during recovery. In summary, these results revealed the existence of a specific pattern of lymphocyte infiltration and cytokine secretion along the different phases of the acute EAE model in Lewis rat that differs from those already described in chronic or relapsing-remitting mouse models, where Th17-cells were found mostly during the peak, suggesting a specific role of these lymphocytes and cytokines in the evolution of this acute EAE model.

Regulation of bone by the adaptive immune system in arthritis

Studies on the immune regulation of osteoclasts in rheumatoid arthritis have promoted the new research field of 'osteoimmunology', which investigates the interplay between the skeletal and immune systems at the molecular level. Accumulating evidence lends support to the theory that bone destruction associated with rheumatoid arthritis is caused by the enhanced activity of osteoclasts, resulting from the activation of a unique helper T cell subset, 'Th17 cells'. Understanding the interaction between osteoclasts and the adaptive immune system in rheumatoid arthritis and the molecular mechanisms of Th17 development will lead to the development of potentially effective therapeutic strategies.

IL-6 induced by Staphylococcus aureus infection prevents the induction of skin allograft acceptance in mice

Clinical correlations between bacterial infections and rejection suggest a hypothesis that innate immune stimulation by bacterial infections results in the production of inflammatory cytokine that facilitate bystander T-cell activation, increased alloreactivity and inhibition of tolerance induction. Previous studies demonstrated that IFNβ produced during an infection with a model bacterium, Listeria monocytogenes, prevented the induction of transplantation tolerance in mice with anti-CD154 and donor-specific transfusion (DST) (1). We investigated the impact of two clinically relevant bacterial infections at the time of transplantation on the ability of anti-CD154 and DST to induce skin allograft acceptance in mice. Staphylococcus aureus (SA) infection prevented skin allograft acceptance whereas maximally tolerated doses of Pseudomonas aeruginosa infection had no effect. SA induced an acute production of IL-6, which was necessary and sufficient for the prevention of skin allograft acceptance. Furthermore, a single pulse of methylprednisolone modulated IL-6 production during SA infection and facilitated skin allograft acceptance in SA-infected recipients. Taken together, our results suggest that bacterial infections elicit specific proinflammatory cytokines signatures that can serve as barriers to tolerance induction, and that inhibiting the production of or neutralizing these inflammatory cytokines can synergize with costimulatory blockade-based therapies to facilitate the development of transplantation tolerance.

Anti-ribosomal P protein antibody induces Th1 responses by enhancing the production of IL-12 in activated monocytes

Autoantibodies to ribosomal P proteins (anti-P) are detected in 12-16% of patients with systemic lupus erythematosus (SLE), and have been found to be associated with some manifestations, including lupus psychosis, nephritis and hepatitis. We have recently disclosed that anti-P react with activated human peripheral blood monocytes, and enhance their production of tumor necrosis factor-α and interleukin (IL)-6. It is also possible that anti-P might regulate other monocyte functions, including the regulation of T helper (Th) responses. The current study was therefore undertaken to explore the effects of anti-P on the induction of Th1 responses. Peripheral blood mononuclear cells (PBMC) from healthy donors were cultured with affinity-purified anti-P or control IgG. Highly purified monocytes were cultured with interferon (IFN)-γ in the presence of anti-P or normal IgG. Anti-P significantly enhanced the production of IFN-γ by PBMC. Of note, anti-IL-12 monoclonal antibodies almost completely abrogated the anti-P-mediated upregulation of the IFN-γ production of PBMC. Accordingly, anti-P significantly enhanced the production of IL-12 by activated monocytes. These results indicate that anti-P induce Th1 responses by upregulating the production of IL-12 by activated monocytes. The data therefore suggest that anti-P play an important role in the pathogenesis of SLE through the promotion of Th1 responses.

Phosphorylation of IRF4 by ROCK2 regulates IL-17 and IL-21 production and the development of autoimmunity in mice

Deregulated production of IL-17 and IL-21 plays a key pathogenic role in many autoimmune disorders. A delineation of the mechanisms that underlie the inappropriate synthesis of IL-17 and IL-21 in autoimmune diseases can thus provide important insights into potential therapies for these disorders. Here we have shown that the serine-threonine kinase Rho-associated, coiled-coil-containing protein kinase 2 (ROCK2) becomes activated in mouse T cells under Th17 skewing conditions and phosphorylates interferon regulatory factor 4 (IRF4), a transcription factor that is absolutely required for the production of IL-17 and IL-21. We furthermore demonstrated that ROCK2-mediated phosphorylation of IRF4 regulated the synthesis of IL-17 and IL-21 and the differentiation of Th17 cells. Whereas CD4+ T cells from WT mice activated ROCK2 physiologically under Th17 conditions, CD4+ T cells from 2 different mouse models of spontaneous autoimmunity aberrantly activated ROCK2 under neutral conditions. Moreover, administration of ROCK inhibitors ameliorated the deregulated production of IL-17 and IL-21 and the inflammatory and autoantibody responses observed in these autoimmune mice. Our findings thus uncover a crucial link among ROCK2, IRF4, and the production of IL-17 and IL-21 and support the idea that selective inhibition of ROCK2 could represent an important therapeutic regimen for the treatment of autoimmune disorders.

Immune modulation by chondroitin sulfate and its degraded disaccharide product in the development of an experimental model of multiple sclerosis

Clinical symptoms in MOG-induced EAE mice significantly exacerbated following chondroitin sulfate A (CS-A) injection, whereas administration of a degraded product, CSPG-DS, caused dramatic inhibition of EAE development. Also, administration of CSPG-DS but not CS-A, after the onset of clinical symptoms of EAE, was able to suppress the disease. Further studies demonstrated that CS-A up-regulated STAT4 expression and thus, induced IFN-gamma production and Th1 CD4 T cell differentiation. CS-A also up-regulated STAT3 and IL-23 expression and thus increased IL-17 producing T cells. CSPG-DS treatment both in vivo and in vitro decreased TNFalpha production from splenocytes. In vitro and in vivo studies indicated that CSPG-DS treatment in EAE mice significantly blocked migration of lymphocytes, whereas CS-A treatment increased lymphocyte infiltration in the brain.

IRF4 and its regulators: evolving insights into the pathogenesis of inflammatory arthritis?

Accumulating evidence from murine and human studies supports a key role for interleukin-17 (IL-17) and IL-21 in the pathogenesis of inflammatory arthritis. The pathways and molecular mechanisms that underlie the production of IL-17 and IL-21 are being rapidly elucidated. This review focuses on interferon regulatory factor 4 (IRF4), a member of the IRF family of transcription factors, which has emerged as a crucial controller of both IL-17 and IL-21 production. We first outline the complex role of IRF4 in the function of CD4(+) T cells and then discuss recent studies from our laboratory that have revealed a surprising role for components of Rho GTPase-mediated pathways in controlling the activity of IRF4. A better understanding of these novel pathways will hopefully provide new insights into mechanisms responsible for the development of inflammatory arthritis and potentially guide the design of novel therapeutic approaches.

STATs in cancer inflammation and immunity: a leading role for STAT3

Commensurate with their roles in regulating cytokine-dependent inflammation and immunity, signal transducer and activator of transcription (STAT) proteins are central in determining whether immune responses in the tumour microenvironment promote or inhibit cancer. Persistently activated STAT3 and, to some extent, STAT5 increase tumour cell proliferation, survival and invasion while suppressing anti-tumour immunity. The persistent activation of STAT3 also mediates tumour-promoting inflammation. STAT3 has this dual role in tumour inflammation and immunity by promoting pro-oncogenic inflammatory pathways, including nuclear factor-kappaB (NF-kappaB) and interleukin-6 (IL-6)-GP130-Janus kinase (JAK) pathways, and by opposing STAT1- and NF-kappaB-mediated T helper 1 anti-tumour immune responses. Consequently, STAT3 is a promising target to redirect inflammation for cancer therapy.

Recent advances in neutralizing the IL-6 pathway in arthritis

Recent advances in understanding the mechanism(s) of how IL-6 trans-signaling regulates immune cell function and promotes inflammation in autoimmune arthritis are critically reviewed. Serum and/or synovial fluid (SF) IL-6 is markedly elevated in adult and juvenile rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS) and osteoarthritis (OA). IL-6, in concert with IL-17, determines the fate of CD4⁺ lymphocytes and therefore TH₁₇ cell differentiation. IL-6 also plays a critical role in modulating B-lymphocyte activity. The recognition that IL-6 trans-signaling regulates inflammation resulted in the development of tocilizumab, a fully humanized monoclonal antibody that neutralizes the biological activity of the IL-6-receptor (IL-6R). Significant clinical benefit was demonstrated as well as reduced serum IL-6 levels with suppression of X-ray progression of disease in several clinical trials in which juvenile or adult RA patients were treated with tocilizumab monotherapy or tocilizumab plus methotrexate. However, levels of serum and/or SF IL-6 cytokine protein superfamily members, adiponectin, oncostatin M, pre-B-cell colony enhancing factor/visfatin and leukemia inhibitory factor are also elevated in RA. Additional studies will be required to determine if anti-IL-6 trans-signaling inhibition strategies with tocilizumab or recombinant soluble IL-6R reduce the level of these cytokines.

STAT3 in CD4+ T helper cell differentiation and inflammatory diseases

Jak/STAT pathways influence cell-fate decisions made by differentiating naïve T cells, regulate the intensity and duration of inflammatory responses and are implicated in pathogenic mechanisms of a number of chronic inflammatory diseases. Among the STATs, the STAT3 protein has emerged as an important determinant of whether the naïve T cell differentiates into regulatory (Treg) or an inflammatory (Th17) T cell lineage. STAT3 also has potent anti-inflammatory effects and regulates critical cellular processes such as, cell growth, apoptosis and transcription of inflammatory genes. Dysregulation of STAT3 pathway has therefore been implicated in the development of chronic inflammatory diseases, as well as, a number of malignant and neurodegenerative diseases. This review focuses on recent findings regarding the role of STAT3 in immunity, with particular emphasis on T cell lineage specification and disease etiology. New insights from animal models of uveitis, multiple sclerosis and inflammatory bowel diseases are discussed as exemplars of critical roles that STAT3 pathways play in inflammatory diseases and on how inhibiting STAT3 can be exploited to mitigate pathogenic autoimmunity.

Th17 cytokines and their emerging roles in inflammation and autoimmunity

T-helper 17 (Th17) cells are a new lineage of CD4(+) T cells that are characterized by their production of interleukin-17A (IL-17A). Recent studies show that these cells can also express IL-17F, IL-22, and IL-21. IL-17A and IL-17F can form a heterodimeric cytokine, which mediates biological activities, at least in part, through shared receptors with IL-17A and IL-17F homodimers. The cytokines made by Th17 cells represent three distinct gene families, highlighting the unique biology of these cells. Accumulating data support a role for Th17 cells and these cytokines in inflammatory processes and in animal models of autoimmunity or inflammation. Emerging data in clinical trials support our understanding of the importance of Th17 cells in inflammatory disease. Future clinical studies will allow us to evaluate the role of each cytokine independently in contributing to human diseases with immune-mediated pathologies and to design optimal cytokine-targeted therapies for these diseases.