Letter: pathogenicity of Th17 cells may differ in ulcerative colitis compared with Crohn's disease

N-ethyl-N-nitrosourea (ENU)-induced C-terminal truncation of Runx3 results in autoimmune colitis associated with Th17/Treg imbalance

Inflammatory bowel disease (IBD) is a chronic and progressive inflammatory intestinal disease that affects people around the world. The primary cause of IBD is an imbalance in the host immune response to intestinal flora. Several human genes, including IL10, STAT3, IRGM, ATG16L1, NOD2 and RUNX3, are associated with inappropriate immune responses in IBD. It has been reported that homozygous Runx3-knockout (ko) mice spontaneously develop colitis. However, the high mortality rate in these mice within the first two weeks makes it challenging to study the role of Runx3 in colitis. To address this issue, a spontaneous colitis (SC) mouse model carrying a C-terminal truncated form of Runx3 with Tyr319stop point mutation has been generated. After weaning, SC mice developed spontaneous diarrhea and exhibited prominent enlargement of the colon, accompanied by severe inflammatory cell infiltration. Results of immunofluorescence staining showed massive CD4+ T cell infiltration in the inflammatory colon of SC mice. Colonic IL-17A mRNA expression and serum IL-17A level were increased in SC mice. CD4+ T cells from SC mice produced stronger IL-17A than those from wildtype mice in Th17-skewing conditions in vitro. In addition, the percentages of Foxp3+ Treg cells as well as the RORγt+Foxp3+ Treg subset, known for its role in suppressing Th17 response in the gut, were notably lower in colon lamina propria of SC mice than those in WT mice. Furthermore, transfer of total CD4+ T cells from SC mice, but not from wildtype mice, into Rag1-ko host mice resulted in severe autoimmune colitis. In conclusion, the C-terminal truncated Runx3 caused autoimmune colitis associated with Th17/Treg imbalance. The SC mouse model is a feasible approach to investigate the effect of immune response on spontaneous colitis.

Kuijieling decoction regulates the Treg/Th17 cell balance in ulcerative colitis through the RA/RARα signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Ulcerative colitis (UC) is an idiopathic intestinal disease characterized by chronic inflammation with unknown etiology. Kuijieling decoction is a traditional Chinese Medicine with unique therapeutic efficacy for UC.

AIM OF THE STUDY

To validate the effects of Kuijieling decoction on vitamin A metabolism and retinoic acid (RA) production, along with evaluation of its immunomodulatory activity, and further clarify the upstream mechanisms underlying Treg/Th17 regulation that contribute to therapeutic effects against UC.

MATERIALS AND METHODS

Network pharmacology and molecular docking analyses were employed to predict the potential anti-UC targets of Kuijieling and associated pathways. A rat model of UC was generated by treatment with trinitrobenzene sulfonic acid (TNBS) to induce inflammation. T lymphocytes were induced to differentiate into Th17 via combined stimulation with the cytokines TGF-β1, IL-6 and IL-23. Expression levels of RA/RARα-related factors (RARα, CRABPII, Smad3, IL-6R and IL-23R) and Treg/Th17 cell-related factors (Foxp3, RORγt) were measured via western blot (WB), quantitative real-time PCR (RT-qPCR), and immunohistochemistry analyses. Components of the vitamin A metabolic pathway (vitamin A, retinol, retinoic acid) and Treg/Th17 cell-related cytokines (IL-10, IL-17, IL-21) were evaluated using ELISA. Flow cytometry was performed to determine the percentages of Treg and Th17 cells.

RESULTS

The action targets of Kuijieling were significantly associated with T cell activation, Th17 cell differentiation and the immune response. IL-2, IL-6, STAT3 and RARα displayed strong binding affinities with the main components of Kuijieling, suggesting an important role in its therapeutic efficacy. Kuijieling promoted vitamin A metabolism and RA/RARα signaling in UC rats and T lymphocytes. Moreover, Kuijieling effectively regulated the Treg/Th17 cell balance in UC rats and T lymphocytes and relieved inflammation. The protective effect of Kuijieling was weakened after inhibition of the RA/RARα signaling pathway.

CONCLUSIONS

Kuijieling promotes vitamin A metabolism and RA synthesis, enhances interactions between RA, intracellular binding protein CRABPII and nuclear receptor RARα, and upregulates Smad3 and Foxp3, thus promoting Treg differentiation. Simultaneously, Kuijieling inhibited expression of IL-6R and IL-23R genes and production of RORγt, leading to suppression of Th17 differentiation, and ultimately, reduction of the Th17/Treg cell ratio.

The involvement of TH17 cells in the pathogenesis of IBD

The pathogenesis of inflammatory bowel disease (IBD) is still unclear. Immune dysfunction may play a key role in the pathogenesis of IBD, in which the role of CD4⁺ T helper (Th) cells is particularly important. Th17 cells are a major component of CD4⁺ T cells, and their differentiation is regulated by a variety of extracellular signals, transcription factors, RNA, and posttranslational modifications. Th17 cells specifically produce IL-17 and play an important role in the protection of mucous membranes and epithelial tissues against infection by extracellular microbes. However, when immune regulation is dysfunctional, Th17 cells abnormally proliferate and produce large amounts of proinflammatory cytokines that can recruit other inflammatory cells, which together induce abnormal immune responses and result in the development of many autoimmune diseases. In recent years, studies have confirmed that Th17 cells play an important role in the pathogenesis of IBD, which makes it a possible target for IBD therapy. This article reviews the recent progress of Th17 cells involved in the pathogenesis of IBD and its targeted therapy.

CD4 T-Cell Subsets and the Pathophysiology of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an umbrella term for the chronic immune-mediated idiopathic inflammation of the gastrointestinal tract, manifesting as Crohn's disease (CD) or ulcerative colitis (UC). IBD is characterized by exacerbated innate and adaptive immunity in the gut in association with microbiota dysbiosis and the disruption of the intestinal barrier, resulting in increased bacterial exposure. In response to signals from microorganisms and damaged tissue, innate immune cells produce inflammatory cytokines and factors that stimulate T and B cells of the adaptive immune system, and a prominent characteristic of IBD patients is the accumulation of inflammatory T-cells and their proinflammatory-associated cytokines in intestinal tissue. Upon antigen recognition and activation, CD4 T-cells differentiate towards a range of distinct phenotypes: T helper(h)1, Th2, Th9, Th17, Th22, T follicular helper (Tfh), and several types of T-regulatory cells (Treg). T-cells are generated according to and adapt to microenvironmental conditions and participate in a complex network of interactions among other immune cells that modulate the further progression of IBD. This review examines the role of the CD4 T-cells most relevant to IBD, highlighting how these cells adapt to the environment and interact with other cell populations to promote or inhibit the development of IBD.

The Double Game Played by Th17 Cells in Infection: Host Defense and Immunopathology

T-helper 17 (Th17) cells represent a subpopulation of CD4+ T lymphocytes that play an essential role in defense against pathogens. Th17 cells are distinguished from Th1 and Th2 cells by their ability to produce members of the interleukin-17 (IL-17) family, namely IL-17A and IL-17F. IL-17 in turn induces several target cells to synthesize and release cytokines, chemokines, and metalloproteinases, thereby amplifying the inflammatory cascade. Th17 cells reside predominantly in the lamina propria of the mucosa. Their main physiological function is to maintain the integrity of the mucosal barrier against the aggression of infectious agents. However, in an appropriate inflammatory microenvironment, Th17 cells can transform into immunopathogenic cells, giving rise to inflammatory and autoimmune diseases. This review aims to analyze the complex mechanisms through which the interaction between Th17 and pathogens can be on the one hand favorable to the host by protecting it from infectious agents, and on the other hand harmful, potentially generating autoimmune reactions and tissue damage.

Immunity and Nutrition: The Right Balance in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an increasingly urgent medical problem that strongly impairs quality of life for patients. A global rise in incidence has been observed over the last few decades, with the highest incidence rates recorded in North America and Europe. Still, an increased incidence has been reported in the last ten years in newly industrialized countries in Asia, including China and India, both with more than one billion inhabitants. These data underline that IBD is an urgent global health problem. In addition, it is estimated that between 20% and 30% of IBD patients will develop colorectal cancer (CRC) within their lifetime and CRC mortality is approximately 50% amongst IBD patients. Although the exact etiology of IBD is still being defined, it is thought to be due to a complex interaction between many factors, including defects in the innate and adaptive immune system; microbial dysbiosis, i.e., abnormal levels of, or abnormal response to, the gastrointestinal microbiome; a genetic predisposition; and several environmental factors. At present, however, it is not fully understood which of these factors are the initiators of inflammation and which are compounders. The purpose of this review is to analyze the complex balance that exists between these elements to maintain intestinal homeostasis and prevent IBD or limit adverse effects on people’s health.

Influence of TRAIL Deficiency on Th17 Cells and Colonic Microbiota in Experimental Colitis Mouse Model

BACKGROUND

The abnormalities of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) are implicated in various autoimmune disorders and tumors. This study investigated the influence of TRAIL deficiency on Th17 cells and colonic microbiota in experimental colitis mouse model.

METHODS

Mice were randomly divided into 4 groups: wild-type, TRAIL gene knock-out (TRAIL^-/-), wild-type colitis and TRAIL^-/- colitis groups. Colitis was induced by oral administration of 3.5% dextran sulfate sodium (DSS) for 7 consecutive days. Mice were given scores for disease severity both clinically and histopathologically. Th17 cells in peripheral blood and mesenteric lymph nodes (MLNs) were assessed using flow cytometry. The expression levels of Th17 cell markers IL-17A and ROR-γt were evaluated by quantitative real-time polymerase chain reaction. The colonic samples were also analyzed for microbiota profile by 16s-rDNA gene sequencing on variable V4 region.

RESULTS

Compared with wild-type counterparts, TRAIL^-/- mice developed more severe colitis after DSS treatment. Colitis TRAIL^-/- mice had increased proportion of Th17 cells and elevated mRNA expression levels of IL-17A and ROR-γt in peripheral blood and MLNs compared with colitis wild-type mice. In contrast to colitis wild-type mice, the composition of colonic microbiota was shifted in colitis TRAIL^-/- mice, and was characterized by increased alpha diversity, increased TM7, deferribacteres and tenericutes, and decreased proteobacteria at the phylum level.

CONCLUSIONS

These findings suggested that TRAIL deficiency not only aggravated DSS-induced colitis, but also led to enhanced Th17 cell response and altered colonic microbiota composition.

Pentacyclic triterpene compounds from loquat leaves reduce skin inflammation and epidermal hyperplasia in psoriasis via inhibiting the Th17 cells

Psoriasis is a refractory inflammatory skin disease affecting 2 %-3 % of the world population, characterized by the infiltration and hyper-proliferation of inflammatory cells and aberrant differentiation of keratinocytes. Targeting the IL-23/ Th17 axis has been well recognized as a promising therapeutic strategy, as the IL-23/ Th17 signal plays a vital role in the pathology of psoriasis. Three pentacyclic triterpene compounds isolated from loquat leaves have been reported with significant inhibitory effects on RORγt transcription activity and Th17 cell differentiation, and excellent performance in preventing lupus nephritis pathogenesis. However, the potential effects of these pentacyclic triterpene compounds on psoriasis remain unknown. In this study, we demonstrated the potent therapeutic effects of these pentacyclic triterpene compounds on psoriasis. These three pentacyclic triterpene compounds significantly alleviated skin inflammation as well as aberrant keratinocyte proliferation in an imiquimod-induced mouse psoriasis model. These compounds also inhibited the infiltration of immune cells and the level of pro-inflammatory cytokine in the dermis, as well as the cells number and changed the cytokine profiling expression of Th17 cells. These compounds could reduce the amount of CD4⁺ and CD8⁺ T cells in local lymph node, but not in spleen, which is different from hydrocortisone, the positive control treatment. These results suggest better performance of these compounds than steroids on treating psoriasis with less side effects on the integrated immune system. In summary, our findings uncover the potent therapeutic effects of pentacyclic triterpene compounds on psoriasis, providing potential candidate compounds for drug development.

Retinoid-Related Orphan Receptor RORγt in CD4+ T-Cell-Mediated Intestinal Homeostasis and Inflammation

Retinoic acid-related orphan receptor (ROR)-γt, the master transcription factor of the Th17 subset of CD4⁺ Th cells, is a promising target for treating a host of autoimmune diseases. RORγt plays a vital role in the pathogenesis of inflammatory bowel diseases-Crohn disease and ulcerative colitis-caused by untoward reactivity of the immune system to the components of the intestinal microbiome. The mammalian intestinal tract is a highly complex and compartmentalized organ with specialized functions, and is a privileged site for the generation of both peripherally induced regulatory CD4⁺ T cells (Tregs) and effector Th17 cells. As Th17 cells can be proinflammatory in nature, the equilibrium between effector Th17 and Treg cells is crucial for balancing intestinal homeostasis and inflammation. Recent findings suggest that RORγt, in addition to Th17 cells, is also expressed in peripherally induced, colonic regulatory CD4⁺ T cells. Therefore, RORγt is expressed in both effector and regulatory subsets of CD4⁺ T cells in the intestine. The present review discusses the role of RORγt in cellular and molecular differentiation of Th17 and Treg, and examines how targeting RORγt in inflammatory bowel disease therapy could influence the development of these two diverse subsets of immune cells with opposing functions.

Therapeutic effect of gold nanoparticles on DSS-induced ulcerative colitis in mice with reference to interleukin-17 expression

Ulcerative colitis (UC) is among the most challenging human diseases. Nanotechnology has incontestable promising outcomes in inflammatory bowel diseases. This study aimed to investigate the therapeutic effect of naked gold nanoparticles (AuNPs) on dextran sodium sulphate (DSS) induced ulcerative colitis in mice. We also examined the expression of interleukin-17 (IL-17) following AuNPs treatment. Mice were randomly divided into control, DSS and DSS+ AuNPs groups. Severity of colitis was assessed by disease activity index (DAI) measurement. At the end of the experiment, the final body weights were recorded. The colon was dissected and processed for histopathological examinations by light and electron microscopes. Colon homogenates were prepared for assay of tissue malondialdehyde (MDA) and real-time PCR analysis of IL-17A. Immunohistochemical localization of IL-17A was carried out. Scanning electron microscopy (SEM) and Energy Dispersive X-ray (EDX) detector were used to detect the presence of AuNPs in the colonic tissue of DSS+ AuNPs groups. Our results showed that AuNPs effectively targeted the colonic tissue, and reduced changes induced by DSS. The underlying mechanisms could be related to anti-oxidant effect (as evident by decreasing tissue MDA) and anti-inflammatory potential of AuNPs. Our study draws attention to as a novel therapeutic strategy for treating UC.

Soybean Meal-Induced Intestinal Inflammation in Zebrafish Is T Cell-Dependent and Has a Th17 Cytokine Profile

Currently, inflammatory bowel disease (IBD) is a serious public health problem on the rise worldwide. In this work, we utilized the zebrafish to introduce a new model of intestinal inflammation triggered by food intake. Taking advantage of the translucency of the larvae and the availability of transgenic zebrafish lines with fluorescently labeled macrophages, neutrophils, or lymphocytes, we studied the behavior of these cell types in vivo during the course of inflammation. We established two feeding strategies, the first using fish that were not previously exposed to food (naïve strategy) and the second in which fish were initially exposed to normal food (developed strategy). In both strategies, we analyzed the effect of subsequent intake of a control or a soybean meal diet. Our results showed increased numbers of innate immune cells in the gut in both the naïve or developed protocols. Likewise, macrophages underwent drastic morphological changes after feeding, switching from a small and rounded contour to a larger and dendritic shape. Lymphocytes colonized the intestine as early as 5 days post fertilization and increased in numbers during the inflammatory process. Gene expression analysis indicated that lymphocytes present in the intestine correspond to T helper cells. Interestingly, control diet only induced a regulatory T cell profile in the developed model. On the contrary, soybean meal diet induced a Th17 response both in naïve and developed model. In addition, when feeding was performed in rag1-deficient fish, intestinal inflammation was not induced indicating that inflammation induced by soybean meal is T cell-dependent.

IL-17 and limits of success

Interleukin-17 (IL-17) is a potent proinflammatory cytokine that protects a host against fungal and extracellular bacterial infections. On the other hand, excessive or dysregulated production of IL-17 underlines susceptibility to autoimmune disease. Consequently, blocking IL-17 has become an effective strategy for modulating several autoimmune diseases, including multiple sclerosis (MS), psoriasis, and rheumatoid arthritis (RA). Notably, however, IL-17 blockade remains ineffective or even pathogenic against important autoimmune diseases such as inflammatory bowel disease (IBD). Furthermore, the efficacy of IL-17 blockade against other autoimmune diseases, including type 1 diabetes (T1D) is currently unknown and waiting results of ongoing clinical trials. Coming years will determine whether the efficacy of IL-17 blockade is limited to certain autoimmune diseases or can be expanded to other autoimmune diseases. These efforts include new clinical trials aimed at testing second-generation agents with the goal of increasing the efficiency, spectrum, and ameliorating side effects of IL-17 blockade. Here we briefly review the roles of IL-17 in the pathogenesis of selected autoimmune diseases and provide updates on ongoing and recently completed trials of IL-17 based immunotherapies.

A probiotic complex, rosavin, zinc, and prebiotics ameliorate intestinal inflammation in an acute colitis mouse model

Background

An altered gut microbiota balance is involved in the pathogenesis of inflammatory bowel disease (IBD), and several probiotic strains are used as dietary supplements to improve intestinal health. We evaluated the therapeutic effect of 12 probiotics in combination with prebiotics, rosavin, and zinc in the dextran sodium sulfate (DSS)-induced colitis mouse model.

Methods

The probiotic complex or the combination drug was administered orally to mice with DSS-induced colitis, and the body weight, disease activity index, colon length, and histopathological parameters were evaluated. Also, the combination drug was applied to HT-29 epithelial cells, and the expression of monocyte chemoattractant protein 1 (MCP-1) was evaluated by real-time polymerase chain reaction.

Results

Administration of the combination drug attenuated the severity of DSS-induced colitis. Moreover, the combination drug significantly reduced the levels of the proinflammatory cytokines tumor necrosis factor-α, interleukin (IL)-6, IL-1β, and IL-17, and significantly increased the levels of Foxp3 and IL-10 in colon sections. Additionally, treatment with the combination drug reduced MCP-1 expression in HT-29 cells. Treatment with the combination drug decreased the levels of α-smooth muscle actin and type I collagen compared with vehicle treatment in mice with DSS-induced colitis.

Conclusion

These results suggest that the combination of a probiotic complex with rosavin, zinc, and prebiotics exerts a therapeutic effect on IBD by modulating production of pro- and anti-inflammatory cytokines and the development of fibrosis.

Immunological pathogenesis of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory state of the gastrointestinal tract and can be classified into 2 main clinical phenomena: Crohn's disease (CD) and ulcerative colitis (UC). The pathogenesis of IBD, including CD and UC, involves the presence of pathogenic factors such as abnormal gut microbiota, immune response dysregulation, environmental changes, and gene variants. Although many investigations have tried to identify novel pathogenic factors associated with IBD that are related to environmental, genetic, microbial, and immune response factors, a full understanding of IBD pathogenesis is unclear. Thus, IBD treatment is far from optimal, and patient outcomes can be unsatisfactory. As result of massive studying on IBD, T helper 17 (Th17) cells and innate lymphoid cells (ILCs) are investigated on their effects on IBD. A recent study of the plasticity of Th17 cells focused primarily on colitis. ILCs also emerging as novel cell family, which play a role in the pathogenesis of IBD. IBD immunopathogenesis is key to understanding the causes of IBD and can lead to the development of IBD therapies. The aim of this review is to explain the pathogenesis of IBD, with a focus on immunological factors and therapies.

TH17 Cell and Epithelial Cell Crosstalk during Inflammatory Bowel Disease and Carcinogenesis

The intestine is colonized by hundreds of different species of commensal bacteria, viruses, and fungi. Therefore, the intestinal immune system is constantly being challenged by foreign antigens. The immune system, the commensal microbiota, and the intestinal epithelial surface have to maintain a tight balance to guarantee defense against potential pathogens and to prevent chronic inflammatory conditions at the same time. Failure of these mechanisms can lead to a vicious cycle in which a perpetual tissue damage/repair process results in a pathological reorganization of the normal mucosal surface. This dysregulation of the intestine is considered to be one of the underlying causes for both inflammatory bowel disease (IBD) and colorectal cancer. T_H17 cells have been associated with immune-mediated diseases, such as IBD, since their discovery in 2005. Upon mucosal damage, these cells are induced by a combination of different cytokines, such as IL-6, TGF-β, and IL-1β. T_H17 cells are crucial players in the defense against extracellular pathogens and have various mechanisms to fulfill their function. They can activate and attract phagocytic cells. Additionally, T_H17 cells can induce the release of anti-microbial peptides from non-immune cells, such as epithelial cells. The flip side of the coin is the strong potential of T_H17 cells to be pro-inflammatory and promote pathogenicity. T_H17 cells have been linked to both mucosal regeneration and inflammation. In turn, these cells and their cytokines emerged as potential therapeutic targets both for inflammatory diseases and cancer. This review will summarize the current knowledge regarding the T_H17 cell-enterocyte crosstalk and give an overview of its clinical implications.

The Role of IL-17 and Th17 Lymphocytes in Autoimmune Diseases

The end of twentieth century has introduced some changes into T helper (Th) cells division. The identification of the new subpopulation of T helper cells producing IL-17 modified model of Th1-Th2 paradigm and it was named Th17. High abilities to stimulate acute and chronic inflammation made these cells ideal candidate for crucial player in development of autoimmune disorders. Numerous publications based on animal and human models confirmed their pivotal role in pathogenesis of human systemic and organ-specific autoimmune diseases. These findings made Th17 cells and pathways regulating their development and function a good target for therapy. Therapies based on inhibition of Th17-dependent pathways are associated with clinical benefits, but on the other hand are frequently inducing adverse effects. In this review, we attempt to summarize researches focused on the importance of Th17 cells in development of human autoimmune diseases as well as effectiveness of targeting IL-17 and its pathways in pre-clinical and clinical studies.

Th17 Cells as Potential Probiotic Therapeutic Targets in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) are characterized by wasting and chronic intestinal inflammation triggered by various cytokine-mediated pathways. In recent years, it was shown that T helper 17 (Th17) cells are involved in the pathogenesis of IBD, which makes them an attractive therapeutic target. Th17 cells preferentially produce interleukin (IL)-17A–F as signature cytokines. The role of the interplay between host genetics and intestinal microbiota in the pathogenesis of IBD was demonstrated. Probiotics are live microorganisms that when orally ingested in adequate amounts, confer a health benefit to the host by modulating the enteric flora or by stimulating the local immune system. Several studies indicated the effectiveness of probiotics in preventing and treating IBD (ulcerative colitis, and Crohn’s disease). Furthermore, there is mounting evidence of probiotics selectively targeting the Th17 lineage in the prevention and management of inflammatory and autoimmune diseases such as IBD. This review highlights critical roles of Th17 cells in the pathogenesis of IBD and the rationale for using probiotics as a novel therapeutic approach for IBD through manipulation of Th17 cells. The potential molecular mechanisms by which probiotics modulate Th17 cells differentiation and production are also discussed.

Central role of gimap5 in maintaining peripheral tolerance and T cell homeostasis in the gut

Inflammatory bowel disease (IBD) including Crohn's disease and ulcerative colitis is often precipitated by an abnormal immune response to microbiota due to host genetic aberrancies. Recent studies highlight the importance of the host genome and microflora interactions in the pathogenesis of mucosal inflammation including IBD. Specifically, genome-wide (GWAS) and also next-generation sequencing (NGS)—including whole exome or genome sequencing—have uncovered a large number of susceptibility loci that predispose to autoimmune diseases and/or the two phenotypes of IBD. In addition, the generation of “IBD-prone” animal models using both reverse and forward genetic approaches has not only helped confirm the identification of susceptibility loci but also shed critical insight into the underlying molecular and cellular pathways that drive colitis development. In this review, we summarize recent findings derived from studies involving a novel early-onset model of colitis as it develops in GTPase of immunity-associated protein 5- (Gimap5-) deficient mice. In humans, GIMAP5 has been associated with autoimmune diseases although its function is poorly defined. Here, we discuss how defects in Gimap5 function impair immunological tolerance and lymphocyte survival and ultimately drive the development of CD4⁺ T cell-mediated early-onset colitis.

Imbalances of CD4(+) T-cell subgroups in Crohn's disease and their relationship with disease activity and prognosis

BACKGROUND AND AIM

The CD4(+) T-cell subgroups play central pathophysiological roles in Crohn's disease (CD); however, their clinical relevance requires additional clarification and remains controversial. We investigated their balance in Chinese CD patients and explored their clinical significance.

METHODS

Peripheral blood mononuclear cells and serum were collected from 46 Chinese CD patients and 23 healthy donors. Circulating Treg, Th1, Th2, and Th17 cells were flow cytometrically analyzed. Subgroup-restricted transcription factor expression was determined by real-time polymerase chain reaction. Serum concentrations of the main cytokines produced by each subgroup were measured by cytometric bead arrays or enzyme-linked immunosorbent assay.

RESULTS

Lower Treg proportion (6.0 ± 1.2% vs 7.8 ± 1.5%, P = 0.030), FOXP3 mRNA expression (0.58-fold, P = 0.030), and circulating soluble TGFβ-1 (19.1 ± 9.9 vs 32.7 ± 16.8 ng/mL, P = 0.038) were observed in CD patients versus controls. The Th1 and Th17 proportions were higher in CD patients (17.8 ± 6.6% vs 7.8 ± 1.5%, P < 0.001; and 3.7 ± 1.8% vs 1.8 ± 0.7%, P = 0.022, respectively), as were transcription factors T-bet (4.6-fold, P = 0.043) and RORγt (14-fold, P < 0.001) and related cytokines (P < 0.05). Th2 proportion, GATA3 mRNA expression, and serum interleukin-4 concentration in CD patients were similar to controls (P > 0.05). Treg/Th1 and Treg/Th17 ratios were higher in inactive versus active CD patients (0.6 ± 0.4 vs 0.3 ± 0.1, P = 0.022; and 3.7 ± 2.0 vs 1.7 ± 1.4, P = 0.013, respectively). During follow-up, patients with lower Treg/Th1 and Treg/Th17 ratios were at higher recurrence risk.

CONCLUSIONS

Imbalances among Treg, Th1, and Th17 subgroups were found in Chinese CD patients. Treg/Th1 and Treg/Th17 ratios are associated with disease activity and are potential prognostic indicators for predicting CD recurrence.

Role of Th17 Cells in the Pathogenesis of Human IBD

The gastrointestinal tract plays a central role in immune system, being able to mount efficient immune responses against pathogens, keeping the homeostasis of the human gut. However, conditions like Crohn's disease (CD) or ulcerative colitis (UC), the main forms of inflammatory bowel diseases (IBD), are related to an excessive and uncontrolled immune response against normal microbiota, through the activation of CD4(+) T helper (Th) cells. Classically, IBD was thought to be primarily mediated by Th1 cells in CD or Th2 cells in UC, but it is now known that Th17 cells and their related cytokines are crucial mediators in both conditions. Th17 cells massively infiltrate the inflamed intestine of IBD patients, where they produce interleukin- (IL-) 17A and other cytokines, triggering and amplifying the inflammatory process. However, these cells show functional plasticity, and they can be converted into either IFN- γ producing Th1 cells or regulatory T cells. This review will summarize the current knowledge regarding the regulation and functional role of Th17 cells in the gut. Deeper insights into their plasticity in inflammatory conditions will contribute to advancing our understanding of the mechanisms that regulate mucosal homeostasis and inflammation in the gut, promoting the design of novel therapeutic approaches for IBD.

Novel treatment options for ulcerative colitis

The approved treatment options for patients with ulcerative colitis (UC) are currently limited to mesalamine or immunosuppressants. Patients who do not respond to mesalamine-based therapy can be treated with immunomodulators or anti-TNF antibody therapy. Failure or adverse reactions to these medications leaves the patient with little choice other than colectomy. However, novel insights into the pathogenic drivers of UC have led to new developments in drugs that promise clinical efficacy via modulation of targeted pathways. Given the impending expansion of therapeutic options for patients with UC, clinicians and researchers should be familiar with these mechanisms of action. In addition, the typical 'step-up' treatment paradigm for UC will likely need to be reshaped to allow for a more personalized approach to treating UC.

The role of IL-17-producing Foxp3+ CD4+ T cells in inflammatory bowel disease and colon cancer

The intestinal epithelium and underlying lamina propria contain T cells that play important roles in maintaining colonic homeostasis. These T cells mediate substantial and specific regulation to ensure that pathogenic microorganisms are eliminated while commensal bacteria are tolerated. There is considerable evidence supporting the notion that the altered ratio between Foxp3(+)CD4(+) T regulatory cells and T effector cells in the colonic microenvironment might contribute to the initiation and progression of inflammation and eventually development of colon cancer. Recent findings on the heterogeneity and plasticity of T regulatory cells, such as the identification of IL-17(+)Foxp3(+)CD4(+) and the RORγt(+)Foxp3(+)CD4(+) subsets, in patients with colorectal inflammation and cancer have provided a new twist in our understanding of the pathogenesis of colonic diseases. Phenotypic and functional properties of IL-17-producing Foxp3(+)CD4(+) T cells as well as the significant implications of these cells in the initiation and progression of colorectal diseases are discussed in this review.