Retinoid-related Orphan Receptor Gammat Research Articles

SMURF1 inhibits the Th17 and Th17.1 polarization and improves the Treg/Th17 imbalance in systemic lupus erythematosus through the ubiquitination of RORγt

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease. This study aimed to investigate the role of SMAD specific E3 ubiquitin protein ligase 1 (SMURF1) in the Th17 and Th17.1 differentiation and Treg/Th17 imbalance, which are major factors contributing to the pathogenesis of SLE. SLE patients and healthy individuals were recruited to detect the SMURF1 levels in naïve CD4+ cells from peripheral blood. Purified and expanded naïve CD4+ T cells were employed to evaluate the effects of SMURF1 on Th17 and Th17.1 polarization in vitro. MRL/lpr lupus model was employed to explore the disease phenotype as well as Treg/Th17 balance in vivo. The results showed that SMURF1 was down-regulated in naïve CD4+ T cells in peripheral blood of patients with SLE and in spleen of MRL/lpr mice. SMURF1 overexpression suppressed the polarization of naïve CD4+ T cells toward Th17 and Th17.1 phenotype and down-regulated the expression of retinoid-related orphan receptor-gammat (RORγt). Subsequently, SMURF1 down-regulation aggravated the disease phenotype, inflammation, and the Treg/Th17 imbalance in MRL/lpr mice. Furthermore, we found that SMURF overexpression promoted the ubiquitination and decreases the stability of RORγt. In conclusion, SMURF1 inhibited the polarization of Th17 and Th17.1 cells and improved the Treg/Th17 imbalance in SLE, which was mediated as least partly by the ubiquitination of RORγt.

LncRNA HOTTIP from synovial fibroblast-derived exosomes: A novel molecular target for rheumatoid arthritis through the miR-1908–5p/STAT3 axis

Rheumatoid arthritis (RA) is a chronic inflammation mediated by autoimmune responses. HOTTIP, a long noncoding RNA (lncRNA), participates in cell proliferation and invasion. However, the correlation between HOTTIP and RA remains unclear. Therefore, this study aimed to clarify how HOTTIP works in RA and to investigate its role in the development of RA. Flow cytometry was used to analyze cell cycle progression. Binding between HOTTIP, signal transducer and activator of transcription 3 (STAT3) and miR-1908–5p was demonstrated by dual-luciferase assays. Quantitative real-time polymerase chain reaction (qRT–PCR) was used to measure the expression of T cell differentiation-related proteins. We found that HOTTIP was upregulated in rheumatoid arthritis synovial fibroblasts (RASFs). HOTTIP directly bound to miR-1908–5p and negatively modulated miR-1908–5p expression while positively regulating STAT3. The effects of HOTTIP overexpression on regulating the balance of the Th17/Treg cell ratio were partly reversed by miR-1908–5p overexpression. In addition, in vivo experiments demonstrated that overexpression of HOTTIP aggravated inflammation in RA mice, which was demonstrated by hematoxylin and eosin (HE) staining and the increased expression levels of CD4+ interleukin (IL)-17+, forkhead Box P3 (FOXP3) and retinoid-related orphan receptor gamma-t (RORγt). In summary, our study suggests that HOTTIP plays a damaging role in RA by promoting inflammation, which may be related to the regulation of miR-1908–5p expression and the STAT3 signaling pathway. These results suggest that the regulation of HOTTIP may be a promising therapeutic strategy for RA.

Metabolic Disturbance and Th17/Treg Imbalance Are Associated With Progression of Gingivitis.

ObjectiveThis study sought to explore the role of metabolic disturbance in immunoregulation of gingivitis targeting T helper 17 cells (Th17)/regulatory T cell (Treg).Materials and MethodsA total of 20 gingivitis patients and 19 healthy volunteers were recruited. Quantitative real time polymerase chain reaction (qRT-PCR) was used to evaluate expression patterns of Forkhead box protein P3 (Foxp3), transforming growth factor-β (TGF-β), retinoid-related orphan receptor-gammat (RORγt) and interleukin 17A (IL-17A) in the peripheral blood lymphocytes of subjects across the two groups. Moreover, the enzyme-linked immunosorbent assay (ELISA) technique was used to detect levels of TGF-β, IL-4, IL-6,TL-10 and L-17A secreted in the plasma as well as the SIgA secreted in saliva. Flow cytometry was used to detect the percentage of CD4+CD25+ Foxp3+Treg cells and the percentage of CD4+IL-17A+ Th17 cells in whole blood of subjects in both groups. Gas chromatography-mass spectrometry (GC-MS) was employed to analyze the plasma metabolites in the gingivitis patient group. Statistical analysis was applied to determine whether the plasma metabolites and related metabolic pathways significantly differed between gingivitis patients and healthy controls. Ingenuity pathway analysis (IPA) was employed to identify the potential relation between the metabolites and the Th17 and Treg related pathway.ResultsThe percentages of CD4+IL17A+Th17 cells and IL-17 significantly increased in the peripheral blood in the gingivitis group. Moreover, the upregulation of IL-17A mRNA and RORγt mRNA were also found in the gingivitis group. However, the percentage of CD4+CD25+ Foxp3+Treg cells and Foxp3 mRNA in the whole blood did not significantly change. However, TGF-β mRNA as well as TGF-β, IL-4, IL-6, IL-10 in the periperial blood and SIgA in the saliva were higher in the gingivitis group. Notably, that the ratio of Th17/Treg cells was significantly increased during peripheral circulation. Furthermore, we identified 18 different metabolites which were differentially expressed in plasma between the gingivitis and healthy control groups. Notably, the levels of cholesterol, glycerol 1-octadecanoate, d-glucose, uric acid, cyclohexaneacetic acid, 3-pyridine, tryptophan, and undecane 2,4-dimethyl were significantly up-regulated. whereas the levels of lactic acid, glycine, linoleic acid, monopalmitic acid, glycerol, palmitic acid, pyruvate, 1-(3-methylbutyl)-2,3,4,6-tetramethylbenzene, 1 5-anhydro d-altrol, and boric acid were down-regulated in the gingivitis group, relative to healthy controls. IPA showed that these metabolites are connected to IL17 signaling, TGF-B signaling, and IL10 signaling, which are related closely to Th17 and Treg pathway.ConclusionOverall, these results showed that disturbance to glycolysis as well as amino and fatty acid metabolism are associated with Th17/Treg balance in gingivitis. Impaired immunometabolism may influence some periodontally involved systemic diseases, hence it is a promising strategy in targeted development of treatment therapies.

Effects of CpG oligodeoxynucleotides on the differentiation of Treg/Th17 cells

AimThe balance between Th17 cells and T regulatory (Treg) cells has emerged as a prominent factor in regulating cancer development. However, the effect of CpG oligodeoxynucleotides (ODNs) on the differentiation of Treg/Th17 cells has not been well studied. We sought here to explore the function of CpG ODNs in the differentiation of Tregs and Th17 cells in vitro and in vivo. MethodsMouse spleen cells were cultured with anti-CD3 monoclonal antibodies in vitro. Tregs and Th17 cell differentiation was induced by transforming growth factor (TGF)-β and interleukin (IL)-2, or TGF-β, IL-6, and IL-23, respectively. Then cells were treated with two CpG ODNs, CpG 1982, or CpG 1826. FBL-3-inoculated C57Bl/6 mice were treated with CpG 1826, tumor vaccine, or combination of CpG 1826 and tumor vaccine. After treatment, spleen cells and serum were isolated, and Tregs/Th17 cells were detected by flow cytometry. The expression of forkhead box P3 (Foxp3), retinoid-related orphan receptor gamma-t (RORγt), IL-10, and IL-17 mRNA was measured by real-time PCR, and protein levels were measured by Western blot and enzyme-linked immunosorbent assay. ResultsThe frequency of Treg cells increased significantly (p < 0.05) in the FBL-3-inoculated leukemia mouse model compared with control mice, whereas the frequency of Th17 cells did not change. Median survival of mice after treatment with CpG 1826 and tumor vaccine was significantly prolonged compared with that of control mice (p < 0.05). The frequency of induced Treg cells decreased after treatment with CpG 1826, whereas the frequency of Th17 cells induced by cytokines in vitro and in the murine leukemia model increased following treatment with CpG 1826. Furthermore, after treatment with CpG 1826, the mRNA and protein levels of Foxp3 and IL-10 decreased significantly both in vitro and in vivo (p < 0.05), whereas those of RORγt and IL-17 increased significantly (p < 0.05). ConclusionCpG 1826 may inhibit the differentiation of Treg cells induced by cytokines, promote the differentiation of Th17 cells in vitro and in murine leukemia models, and prolong the median survival of mice with leukemia.

Tocilizumab promotes corneal allograft survival in rats by modulating Treg-Th17 balance.

To examine the therapeutic effects of tocilizumab on experimental corneal transplantation and its effect on Treg/Th17 balance. Allograft corneal graft was performed between host Sprague Dawley and Wistar donor rats. The rats were randomly divided into four groups: normal, autograft, allograft, and allograft treated with tocilizumab. Kaplan-Meier was performed to draw the survival curve. The protein levels of interleukin-17A (IL-17A), vascular endothelial growth factor (VEGF), and forkhead box protein 3 (Foxp3) were measured by immunohistochemistry. The mRNA levels of IL-17A, VEGF, retinoid-related orphan receptor gammat (RORγt), interleukin-6 (IL-6) and Foxp3 were detected by reverse transcription real-time polymerase chain reaction (RT-PCR). The Treg and Th17 cells were investigated by flow cytometry. The survival time of tocilizumab group was (24±1.27d) longer than that of allograft group (10±0.55d). Moreover, immunohistochemical examination revealed that IL-17A and VEGF protein levels in the allograft group were significantly higher than that of tocilizumab group (P<0.01), while Foxp3 levels in the allograft group was significantly lower than that of the tocilizumab treated group (P<0.001). Flow cytometry showed that the number of Th17 cells in allograft group was significantly higher than that in tocilizumab group (P<0.001). Meanwhile, the number of Tregs was significantly lower than in tocilizumab group (P<0.001). Simultaneously, Foxp3 mRNA expression level in corneal tissues of tocilizumab treated group was significantly higher than other groups (P<0.001). These findings suggest that tocilizumab may promote corneal allograft survival, possibly by modulating Treg-Th17 balance.

5,6,7,8-Tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine derivatives as inhibitors of full-length RORγt

Retinoid-related orphan receptor gamma-t (RORγt) belongs to the nuclear receptor superfamily that takes vital roles in the development and maturation of T-helper 17 cell (Th17) and lymph-node genesis. Because Th17 cells have been proved to be major effectors in human autoimmune and inflammatory diseases, the agonists and antagonists of RORγt have been discovered as promising leads for the therapeutics of these diseases. Most of the current studies of RORγt inhibitors have been focused on ligand binding domain (LBD) of RORγt because the structure and binding pockets of LBD have been elucidated and studied in detail. Recent research elucidated that the hinge domain (HD) of RORγt was significantly involved in the SUMOylation of RORγt and thus specifically affecting T cell development but not lymph-node genesis. These discoveries highlighted the potential of HD of RORγt as the target of RORγt inhibitors that could specifically inhibit Th17-related activities without affecting lymph-node genesis. In this study, we utilized a screening system with full-length RORγt including DBD, HD and LBD to evaluate the activities of a synthesized library of tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine derivatives. We identified a potent lead compound (28) that effectively inhibited Th17 cell differentiation. Docking and structure–activity relationship (SAR) studies showed that compound 28 may not bind in the binding pocket as most of the known inhibitors, but may bind in the pocket closed to Gln223 and Leu244 in HD. Our studies showed evidence that the HD of RORγt could afford a binding pocket for Th17 specific inhibitors and this domain should be further studied to discover potent and specific RORγt inhibitors.

Epigallocatechin gallate ameliorates airway inflammation by regulating Treg/Th17 imbalance in an asthmatic mouse model

Epigallocatechin gallate (EGCG) is a polyphenol that is found in green tea that has been shown to ameliorate airway inflammation in an ovalbumin-sensitized asthmatic mouse model. The purpose of this study was to investigate whether the immunomodulatory and anti-inflammatory effects of EGCG by regulating the regulatory T cell (Treg)/Th 17 cells balance in this model. Female BALB/c mice were sensitized and challenged with ovalbumin by intraperitoneal injection. EGCG was administered to asthmatic mice intraperitoneally 1 h before each OVA challenge. Airway hyperresponsiveness (AHR) was measured, and lung inflammatory infiltrations were assessed by hematoxylin and eosin (HE) staining. Serum OVA-specific IgE levels, Interleukin-10 (IL-10) levels and Interleukin-17A (IL-17A) levels in the bronchoalveolar lavage fluid (BALF), serum, and splenocyte culture supernatants were measured by ELISA. Flow cytometry was used to assess the effects of EGCG on the frequency of CD4+CD25+Foxp3+Treg cells in the splenocytes and real-time PCR method was used to measure the expression of Forkhead box P3 (Foxp3) mRNA and retinoid-related orphan receptor gammat (RORγt) mRNA in the lung tissue. The results showed that administration of EGCG significantly decreased AHR and OVA specific IgE in the serum, increased IL-10 levels in the BALF, serum, and splenocyte culture supernatant, and the frequency of CD4+CD25+Foxp3+Treg cells in the splenocytes in asthmatic mice. Administration of EGCG also ameliorated airway inflammation and eosinophil infiltrations in asthmatic mice. These results suggested that EGCG likely ameliorated OVA-induced airway inflammation by increasing the production of IL-10, the number of CD4+CD25+Foxp3+Treg cells and expression of Foxp3 mRNA in the lung tissue, and it could be an effective agent for treating asthma.

Effects of honokiol on particulate matter 2.5-induced lung injury in asthmatic mice and its mechanisms

To explore the therapeutic effect of honokiol on particulate matter 2.5 (PM2.5)-induced lung injury in asthmatic mice and the possible mechanisms. Methods: A total of 32 BALB/C mice were randomly divided into four groups: a normal saline group, a model group, a PM2.5 group and a honokiol group (n=8 in each group). The asthma mouse model was established by ovalbumin treatment. The mice were treated with physiological saline, ovalbumin, PM2.5 and honokiol, respectively. Lung tissues and serum were collected. The pathological changes of lung tissues were evaluated. The levels of inflammatory cytokines in bronchoalveolar lavage fluid (BALF) and serum were measured and the expressions of Toll like receptor 4 (TLR4), nuclear factor kappa B (NF-κB), retinoid-related orphan receptor gamma-t (RORγt) and forkhead box protein 3 (Foxp3) in lung tissues were detected. Results: 1) The lung tissues of mice in the asthma group showed obvious pathological changes and inflammatory state, suggesting that the asthma model was established successfully. PM2.5 could aggravate the pathological condition of inflammatory injury in lung tissues in asthmatic mice. 2) Compared to the PM2.5 group, the pathological symptoms in the lung tissues were alleviated in the honokiol group and the percentage of inflammatory cells in BALF and the levels of inflammatory cytokines in BALF and serum were significantly reduced (all P<0.05). 3) Compared to the PM2.5 group, the expressions of TLR4, NF-κB (p-p65) and RORγt in lung tissues were significantly decreased, while the expression of Foxp3 was increased; the ratio of RORγt/Foxp3 was also decreased in the honokiol group (all P<0.05). Conclusion: Honokiol can resist lung injury induced by PM2.5 in asthmatic mice. These effects are through inhibiting TLR4-NF-κB pathway-mediated inflammatory response or regulating the balance of Th17/Treg cells.

Effects of grape seed proanthocyanidin extract on airway inflammation and Treg/Th17 balance in asthmatic mice

Objective To explore effect of grape seed proanthocyanidin extract(GSPE)on airway inflammation and hyperresponsiveness of ovalbumin-induced murine asthma model and the associated regulatory effect on Treg/Th17 imbalance. Methods A total of 40 mice were randomly assigned to four experimental groups: control, asthma model, low dose GSPE(40 mg/kg), and high dose GSPE(80 mg/kg). Acute asthma model was established with OVA; airway responsiveness of mice in each group was measured with a noninvasive pulmonary function instrument; lung inflammation changes were observed by pathological HE staining; Treg/Th17 cytokines levels in bronchoalveolar lavage fluid were evaluated by ELISA; the expressions of forkhead/winged helix transcription factor(Foxp3)mRNA and retinoid-related orphan receptor gammat(RORγt)mRNA in lung tissue of each group were gained by Real-time PCR method. Results GSPE inhibited ovalbumin-induced increases in airway responsiveness(P<0.05). Histological studies demonstrated that GSPE substantially inhibited OVA-induced airway inflammation in lung tissue.GSPE decreased IL-17A levels and increased IL-10 levels in bronchoalveolar lavage fluid(P<0.05). In the asthma model group, RORγt mRNA expression in lung tissue was significantly higher than that in the control group(P<0.05)and Foxp3 mRNA expression was significantly lower than that in the control group(P<0.05). In the GSPE group, RORγt mRNA expression was lower than that in asthma model group(P<0.05), however the Foxp3 mRNA expression was higher than that in asthma model group(P<0.05). Conclusion GSPE could alleviate airway hyperresponsiveness and airway inflammation of in asthmatic mice.It can modify the asthmatic mice Treg/Th17 imbalance by decreasing IL-17A and increasing IL-10 concentration at the level of cytokines; and also by increasing Foxp3 mRNA expression and inhibiting the expression of RORγt mRNA at the transcriptional level, which provide a new way for treatment of bronchial asthma. Key words: Grape seed proanthocyanidin extract; Asthma; Forkhead/winged helix transcription factor; Retinoid-related orphan receptor gammat

Effects of Thalidomide on Peripheral Blood Th17 Cells of Patients with Multiple Myeloma

To explore the change of T help cell 17 (Th17) in the peripheral blood of patients with multiple myeloma (MM) before and after treatment with thalidomide. A total of 35 MM patients treated with thalidomide and 35 healthy controls were enrolled in this study. The percentage of Th17 cells were detected by flow cytometry. The mRNA levels of retinoid-related orphan receptor gamma-t (RORγt) were detected by real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) and the plasm IL-17 levels were measured by enzyme linked immunosorbent assay (ELISA). The percentage of Th17 cells, the mRNA expression of RORγt and the plasm IL-17 levels in patients with MM were statistically higher than those in normal controls (P < 0.05). The percentage of Th17 cells was not correlate with the sex, age, disease type, globulin, immune globulin, light chain, M-protein and the proportion of plasmocytes (P > 0.05), but correlated with ISS stage, the level of β2-microglobulin and the plasm IL-17 levels (P < 0.05). The percentage of Th17 cells, the mRNA expression of RORγt and the plasm IL-17 levels in patients with response to thalidomide were statistically lower than those in patients before treatment (P < 0.05). The Th17 cells increase in the peripheral blood of patients with MM, the Th17 cells may participate in the occurrence of MM. Thalidomide may exert anti-MM through down-regulating Th17 cells.

The Transcription Factors T-bet and Runx Are Required for the Ontogeny of Pathogenic Interferon-γ-Producing T Helper 17 Cells

T helper 17 (Th17) cells can give rise to interleukin-17A (IL-17A)- and interferon (IFN)-γ-double-producing cells that are implicated in development of autoimmune diseases. However, the molecular mechanisms that govern generation of IFN-γ-producing Th17 cells are unclear. We found that coexpression of the Th1 and Th17 cell master transcription factors, T-bet and retinoid-related orphan receptor gamma-t (RORγt), respectively, did not generate Th cells with robust IL-17 and IFN-γ expression. Instead, development of IFN-γ-producing Th17 cells required T-bet and Runx1 or Runx3. IL-12-stimulated Th17 cells upregulated Runx1, which bound to the Ifng locus in a T-bet-dependent manner. Reciprocally, T-bet or Runx1 deficiency or inhibition of Runx transcriptional activity impaired the development of IFN-γ-producing Th17 cells during experimental autoimmune encephalomyelitis, which correlated with substantially ameliorated disease course. Thus, our studies identify a critical role for T-bet and Runx transcription factors in the generation of pathogenic IFN-γ-producing Th17 cells.

Discovery of Tertiary Amine and Indole Derivatives as Potent RORγt Inverse Agonists.

A novel series of tertiary amines as retinoid-related orphan receptor gamma-t (RORγt) inverse agonists was discovered through agonist/inverse agonist conversion. The level of RORγt inhibition can be enhanced by modulating the conformational disruption of H12 in RORγt LBD. Linker exploration and rational design led to the discovery of more potent indole-based RORγt inverse agonists.

The Inhibitory Receptor BTLA Controls γδ T Cell Homeostasis and Inflammatory Responses

γδ T cells rapidly secrete inflammatory cytokines at barrier sites that aid in protection from pathogens, but mechanisms limiting inflammatory damage remain unclear. We found that retinoid-related orphan receptor gamma-t (RORγt) and interleukin-7 (IL-7) influence γδ T cell homeostasis and function by regulating expression of the inhibitory receptor, B and T lymphocyte attenuator (BTLA). The transcription factor RORγt, via its activating function-2 domain, repressed Btla transcription, whereas IL-7 increased BTLA levels on the cell surface. BTLA expression limited γδ T cell numbers and sustained normal γδ T cell subset frequencies by restricting IL-7 responsiveness and expansion of the CD27(-)RORγt(+) population. BTLA also negatively regulated IL-17 and TNF production in CD27(-) γδ T cells. Consequently, BTLA-deficient mice exhibit enhanced disease in a γδ T cell-dependent model of dermatitis, whereas BTLA agonism reduced inflammation. Therefore, by coordinating expression of BTLA, RORγt and IL-7 balance suppressive and activation stimuli to regulate γδ T cell homeostasis and inflammatory responses.

CORRIGENDUM

Invariant natural killer T (iNKT) cells play a protective role in the development of certain autoimmune diseases. However, their precise role in the pathogenesis of autoimmune arthritis remains unclear. In this study, we examined the possible contribution of iNKT cells in collagen-induced arthritis (CIA) by using iNKT cell-deficient mice (Jalpha281-/- mice). CIA in these mice was markedly suppressed and interleukin (IL)-17 production was reduced in a native type II collagen (CII)-specific T cell response. Draining lymph nodes of CII-immunized Jalpha281-/- mice contained a significantly low number of IL-17-producing T helper cells. To determine whether iNKT cells produce IL-17, we measured IL-17 by enzyme-linked immunosorbent assay in iNKT cells stimulated with the ligand, alpha-galactosylceramide (alpha-GalCer). Notably, splenocytes from Jalpha281-/- mice stimulated in this way were negative for IL-17, whereas those from C57BL/6 mice produced IL-17. Immunostaining for IL-17 in iNKT cells confirmed intracellular staining of the protein. RT-PCR analysis showed that iNKT cells expressed retinoid-related orphan receptor gammaT and IL-23 receptor. Moreover, cell sorting demonstrated that NK1.1- iNKT cells were the main producers of IL-17 compared with NK1.1+ iNKT cells. IL-17 production by iNKT cells was induced by IL-23-dependent and -independent pathways, since iNKT produced IL-17 when stimulated with either IL-23 or alpha-GalCer alone. Our findings indicate that iNKT cells are producers and activators of IL-17 via IL-23- dependent and -independent pathways, suggesting that they are key cells in the pathogenesis of CIA through IL-17.

Gfi1 negatively regulates Th17 differentiation by inhibiting ROR t activity

T(h) cells have long been divided into two subsets, T(h)1 and T(h)2; however, recently, T(h)17 and inducible regulatory T (iTreg) cells were identified as new T(h) cell subsets. Although T(h)1- and T(h)2-polarizing cytokines have been shown to suppress T(h)17 and iTreg development, transcriptional regulation of T(h)17 and iTreg differentiation by cytokines remains to be clarified. In this study, we found that expression of the growth factor independent 1 (Gfi1) gene, which has been implicated in T(h)2 development, was repressed in T(h)17 and iTreg cells compared with T(h)1 and T(h)2 lineages. Gfi1 expression was enhanced by the IFN-gamma/STAT1 and IL-4/STAT6 pathways, whereas it was repressed by the transforming growth factor-beta1 stimulation at the promoter level. Over-expression of Gfi1 strongly reduced IL-17A transcription in the EL4 T cell line, as well as in primary T cells. This was due to the blockade of recruitment of retinoid-related orphan receptor gammat to the IL-17A promoter. In contrast, IL-17A expression was significantly enhanced in Gfi1-deficient T cells under T(h)17-promoting differentiation conditions as compared with wild-type T cells. In contrast, the impacts of Gfi1 in iTregs were not as strong as in T(h)17 cells. Taken together, these data strongly suggest that Gfi1 is a negative regulator of T(h)17 differentiation, which represents a novel mechanism for the regulation of T(h)17 development by cytokines.

Th17 cells: from precursors to players in inflammation and infection.

Upon activation, naive CD4(+) T cells differentiate into different lineages of effector T(h) subsets. Each subset is characterized by its unique cytokine profile and biological functions. T(h)17, a newly described T(h) subset that produces IL-17, IL-17F and IL-22 in preference to other cytokines, has been shown to play an important role in clearing specific pathogens and in inducing autoimmune tissue inflammations. Over the last 2-3 years, significant progress has been made to understand the development and biological functions of T(h)17 subset. Transforming growth factor beta (TGF) together with IL-6 or IL-21 initiates the differentiation while IL-23 stabilizes the generation of T(h)17 cells. The transcription factors of T(h)17 cells [retinoid-related orphan receptor (ROR) gammat, ROR-alpha and signal transducer and activator of transcription-3] have been described recently. Since TGF-beta is essential for the generation of both T(h)17 and regulatory T (T(reg)) cells from naive T cells, which suggests a developmental link between T(h)17 and T(reg) cells. Functions of these two subsets of T cells are, however, opposite to each other; T(h)17 cells are highly pathogenic during the inflammatory process while T(reg) cells are crucial for inhibiting tissue inflammation and maintaining self-tolerance. Here, we review the recent information on differentiation and effector functions of T(h)17 cells during inflammatory conditions.

Common themes emerge in the transcriptional control of T helper and developmental cell fate decisions regulated by the T-box, GATA and ROR families.

Cellular differentiation requires the precise action of lineage-determining transcription factors. In the immune system, CD4(+) T helper cells differentiate into at least three distinct effector lineages, T helper type 1 (Th1), Th2 and Th17, with the fate of the cell at least in part determined by the transcription factors T-box expressed in T cells (T-bet), GATA-3 and retinoid-related orphan receptor gammat (RORgammat), respectively. Importantly, these transcription factors are members of larger families that are required for numerous developmental transitions from early embryogenesis into adulthood. Mutations in members of these transcription factor families are associated with a number of human genetic diseases due to a failure in completing lineage-specification events when the factor is dysregulated. Mechanistically, there are both common and distinct functional activities that are utilized by T-box, GATA and ROR family members to globally alter the cellular gene expression profiles at specific cell fate decision checkpoints. Therefore, understanding the molecular events that contribute to the ability of T-bet, GATA-3 and RORgammat to define T helper cell lineages can provide valuable information relevant to the establishment of other developmental systems and, conversely, information from diverse developmental systems may provide unexpected insights into the molecular mechanisms utilized in T helper cell differentiation.