Balance of Th1 and Th17 effector and peripheral regulatory T cells

Transfer of antigen-specific T cells into antigen-expressing lymphopenic recipients leads to the sequential generation of Th1 and Th17 effector and protective CD25⁺FoxP3⁺ regulatory cells in the periphery with surprisingly different kinetics. Such an experimental model is potentially valuable for defining the stimuli that regulate lineage decision and plasticity of various T cell effectors and peripheral regulatory T cells. Our studies have shown that IL-17 production occurs rapidly and declines within the first week with the appearance of IFN-γ producing T cells. Regulatory T cells appear during the recovery phase of the disease. The factors that mediate this complex differentiation originating from a starting naïve T cell population remain to be defined.     

Pyruvate dehydrogenase fuels a critical citrate pool that is essential for Th17 cell effector functions

1. Download : Download high-res image (111KB)
2. Download : Download full-size image

     

Ex vivo analysis of pancreatic cancer-infiltrating T lymphocytes reveals that ENO-specific Tregs accumulate in tumor tissue and inhibit Th1/Th17 effector cell functions

Pancreatic cancer (PC) is an aggressive disease with dismal prognosis. Surgical resection is the recommended treatment for long-term survival, but patients with resectable PC are in the minority (with a 5-year survival rate of 20 %). Therefore, development of novel therapeutic strategies, such as anti-PC immunotherapy, is crucial. α-Enolase (ENO1) is an enzyme expressed on the surface of pancreatic cancer cells and is able to promote cell migration and cancer metastasis. The capacity of ENO1 to induce an immune response in PC patients renders it a true tumor-associated antigen. In this study, we characterized the effector functions of ENO1-specific T cells isolated from PC patients, and we specifically evaluated the successful role of intra-tumoral T helper 17 (Th17) cells and the inhibitory role of regulatory T (Tregs) cells in respectively promoting or reducing the cancer-specific immune response. In this ex vivo study, we have demonstrated, for the first time, that ENO1-specific Th17 cells have a specific anti-cancer effector function in PC patients, and that there are decreased levels of these cells in cancer compared to healthy mucosa. Conversely, there are elevated levels of ENO1-specific Tregs in PC patients which lead to inhibition of the antigen-specific effector T cells, thus highlighting a possible role in promoting PC progression. These results may be relevant for the design of novel immunotherapeutic strategies in pancreatic cancer.     

Cutting edge: TLR2 directly triggers Th1 effector functions

Toll-like receptors recognize pathogen-associated molecular patterns, activate innate immunity, and consequently modulate adaptive immunity in response to infections. TLRs are also expressed on T cells, and it has been shown that T cell activation is modulated by TLR ligands. However, the functions of TLRs on Th1 and Th2 effector cells and the molecular mechanisms underlying TLR-mediated activation are not fully understood. We analyzed TLR functions and downstream signaling events in both effector T cells. In mouse Th1 cells the stimulation by TLR2 but not by other TLRs directly induced IFN-gamma production, cell proliferation, and cell survival without TCR stimulation, and these effects were greatly enhanced by IL-2 or IL-12 through the enhanced activation of MAPKs. In contrast, no TLR affected the function of effector Th2 cells. These results identify TLR2 as a new specific activator of Th1 cell function and imply the involvement in Th1-mediated responses.     

Generation and immunologic functions of Th17 cells in malignant gliomas

Th17 cells, a recently discovered inflammatory T cell subtype, have been implicated with autoimmune disorders. However, mechanism of generation or functions of intratumoral Th17 cells are still unclear. We have been investigating the mechanism of induction and role of Th17 cells in malignant gliomas using primary tumor as well as cell lines. We report here that: (1) a higher frequency of Th17 cells in gliomas were associated with higher number of myeloid (CD11b) cells as well as the expression of TGF-β1 or IL-6; (2) conditioned medium from glioma cells (Gl CM) induced Th17 cell differentiation, which was inhibited by anti-TGF-β1 and anti-IL-6; (3) glioma-associated monocytes secreted Th17-promoting cytokines IL-1β and IL-23; (4) CM from glioma and monocyte co-culture (Gl+Mo CM) induced high frequency of Th17 cells in naïve T cell culture, which was abrogated by anti-IL-1β and anti-IL-23 antibodies; (5) In vitro Gl+Mo CM-mediated Th17 generation was associated with a decrease in IFN-γ and a concomitant increase in IL-10 secretion. Anti-TGF-β1, but not anti-IL-6, significantly reversed this cytokine profile. These results demonstrate prevalence of Th17 cells in gliomas and implicate the cytokines derived from the tumor as well as infiltrating myeloid cells in the induction of Th17 cells in glioma microenvironment. Moreover, the data also suggest that glioma-associated Th17 cells may contribute to immune-suppression via TGF-β1-induced IL-10 secretion. Further studies on the mechanism of tumor-infiltration, developmental pathways, and pro-/anti-tumor functions of Th17 cells will provide rationale for developing novel adjuvant immunotherapeutic strategies for malignant gliomas.     

Cutting edge: CD94/NKG2 is expressed on Th1 but not Th2 cells and costimulates Th1 effector functions

Th1 and Th2 cells can be phenotypically distinguished by very few cell surface markers. To identify cell surface molecules that are specifically expressed on Th1 cells, we have generated a panel of mAbs that specifically bind the surfaces of murine Th1 but not Th2 cells. One of these Abs identified the NK cell receptor CD94 as a molecule also specifically expressed on the surface of Th1 cells. As in NK cells, CD94 is expressed on Th1 cells together with members of the NKG2 family of molecules, including NKG2A, C, and E. Cross-linking these receptors on differentiated Th1 cells in vitro costimulates proliferation and cytokine production with a potency similar to that obtained by cross-linking CD28. We propose that CD94/NKG2 heterodimers may costimulate effector functions of differentiated Th1 cells.     

Stem-like intestinal Th17 cells give rise to pathogenic effector T cells during autoimmunity

1. Download : Download high-res image (193KB)
2. Download : Download full-size image

     

Th1, Th2, and Th17 effector T cell-induced autoimmune gastritis differs in pathological pattern and in susceptibility to suppression by regulatory T cells

Th cells can be subdivided into IFN-gamma-secreting Th1, IL-4/IL-5-secreting Th2, and IL-17-secreting Th17 cells. We have evaluated the capacity of fully differentiated Th1, Th2, and Th17 cells derived from a mouse bearing a transgenic TCR specific for the gastric parietal cell antigen, H(+)K(+)-ATPase, to induce autoimmune gastritis after transfer to immunodeficient recipients. We have also determined the susceptibility of the disease induced by each of the effector T cell types to suppression by polyclonal regulatory T cells (Treg) in vivo. Each type of effector cell induced autoimmune gastritis with distinct histological patterns. Th17 cells induced the most destructive disease with cellular infiltrates composed primarily of eosinophils accompanied by high levels of serum IgE. Polyclonal Treg could suppress the capacity of Th1 cells, could moderately suppress Th2 cells, but could suppress Th17-induced disease only at early time points. The major effect of the Treg was to inhibit the expansion of the effector T cells. However, effector cells isolated from protected animals were not anergic and were fully competent to proliferate and produce effector cytokines ex vivo. The strong inhibitory effect of polyclonal Treg on the capacity of some types of differentiated effector cells to induce disease provides an experimental basis for the clinical use of polyclonal Treg in the treatment of autoimmune disease in humans.     

Suppressive effect of IL-27 on encephalitogenic Th17 cells and the effector phase of experimental autoimmune encephalomyelitis

IL-27 has been shown to play a suppressive role in experimental autoimmune encephalomyelitis (EAE) as demonstrated by more severe disease in IL-27R-deficient (WSX-1(-/-)) mice. However, whether IL-27 influences the induction or effector phase of EAE is unknown. This is an important question as therapies for autoimmune diseases are generally started after autoreactive T cells have been primed. In this study, we demonstrate maximal gene expression of IL-27 subunits and its receptor in the CNS at the effector phases of relapsing-remitting EAE including disease peak and onset of relapse. We also show that activated astrocyte cultures secrete IL-27p28 protein which is augmented by the endogenous factor, IFN-gamma. To investigate functional significance of a correlation between gene expression and disease activity, we examined the effect of IL-27 at the effector phase of disease using adoptive transfer EAE. Exogenous IL-27 potently suppressed the ability of encephalitogenic lymph node and spleen cells to transfer EAE. IL-27 significantly inhibited both nonpolarized and IL-23-driven IL-17 production by myelin-reactive T cells thereby suppressing their encephalitogenicity in adoptive transfer EAE. Furthermore, we demonstrate a strong suppressive effect of IL-27 on active EAE in vivo when delivered by s.c. osmotic pump. IL-27-treated mice had reduced CNS inflammatory infiltration and, notably, a lower proportion of Th17 cells. Together, these data demonstrate the suppressive effect of IL-27 on primed, autoreactive T cells, particularly, cells of the Th17 lineage. IL-27 can potently suppress the effector phase of EAE in vivo and, thus, may have therapeutic potential in autoimmune diseases such as multiple sclerosis.     

IL-17 and Th17 cells in tuberculosis

Tuberculosis is primarily a disease of the lung. Constant expression of cellular immunity in this organ is required to control Mycobacterium tuberculosis growth, but this can also result in chronic inflammation and pathologic consequences. During primary tuberculosis both IFN-γ and IL-17 are induced: both are potent inflammatory cytokines capable of inducing expression of chemokines that promote cell recruitment and granuloma organization throughout infection. During the chronic phase, a balance between Th1 and Th17 responses needs to be achieved to control bacterial growth and limit immunopathology, as a shift of the response towards excessive IL-17 production may sustain extensive neutrophil recruitment and tissue damage. Thus, regulation of Th1 and Th17 responses during tuberculosis is essential to promote anti-mycobacterial immunity and prevent extensive immunopathological consequences.     

CD226 is specifically expressed on the surface of Th1 cells and regulates their expansion and effector functions

Surface molecules that are differentially expressed on Th1 and Th2 cells may be useful in regulating specific immune responses in vivo. Using a panel of mAbs, we have identified murine CD226 as specifically expressed on the surface of differentiated Th1 cells but not Th2 or Th0 cells. Although CD226 is constitutively expressed on CD8 cells, it is up-regulated on CD4 cells upon activation. Th1 differentiation results in enhanced CD226 expression, whereas expression is down-regulated upon Th2 polarization. We demonstrate that CD226 is involved in the regulation of T cell activation; in vivo treatment with anti-CD226 results in significant reduction of Th1 cell expansion and in the induction of APCs that inhibit T cell activation. Furthermore, anti-CD226 treatment delays the onset and reduces the severity of a Th1-mediated autoimmune disease, experimental autoimmune encephalomyelitis. Our data suggest that CD226 is a costimulatory molecule that plays an important role in activation and effector functions of Th1 cells.     

Diversity and flexibility of sex-change strategies in animals

Here, we review recent empirical advances that have improved our understanding of why and when sex change occurs. We show that sex-changing animals use a greater diversity of strategies to increase their reproductive success than was previously recognized: some individuals change sex early, others change sex late, some individuals change sex more than once, and others do not change sex at all. These different strategies can be unified by the principle that individuals change sex when it increases their reproductive value. The breeding tactics (male, female or non-breeder) adopted by individuals often appear to be adaptive responses to their own social-ecological context and variation in these conditions results in significant differences in the timing of sex change within and between species.     

Change of Th17 Lymphocytes and Treg/Th17 in Typical and Atypical Optic Neuritis

Background

Typical and atypical optic neuritis (ON) are two clinical types of autoimmune inflammatory diseases of the optic nerve that causes acute vision loss, and are difficult to distinguish in their early stages. The disturbance in the balance of Th17 and Treg lymphocytes is thought to play an essential role in these autoimmune inflammatory diseases.

Objectives

To detect the clinical relevance of Th17 and Treg in peripheral blood and the ratio of Treg/Th17 in patients with typical and atypical ON. To determine whether analysis of Th17 and Treg lymphocytes will provides insights into the different disease phenotypes of typical and atypical ON.

Methods

We studied a consecutive series of patients aged 14–70 years who presented to our neurological department with typical ON (n = 30) or atypical ON (n = 33) within 4 weeks of their acute attacks. Routine clinical tests and ophthalmological examination were performed in all patients. Blood samples were collected from untreated patients and from gender- and age-matched healthy controls (n = 30). The proportion of peripheral blood Th17 cells and Treg cells was determined by flow cytometry.

Results

Patients with atypical ON had a higher proportion of Th17 cells than patients with typical ON (3.61±1.56 vs 2.55±1.74, P<0.01) or controls (1.45±0.86, P<0.01). The proportion of Th17 cells in patients with typical ON was also markedly higher than in controls (P<0.01). The mean percentage of Treg cells in atypical ON (6.31±2.11) and typical ON (6.80±2.00) were significantly lower when compared to controls (8.29±2.32, both P<0.01). No significant difference in Treg frequency was observed between typical ON and atypical ON (p>0.05).

Conclusions

The frequency of Th17 cells is higher in atypical ON than typical ON, and patients with atypical ON have a greater imbalance of pro-inflammatory and regulatory cells than patients with typical ON when compared with controls. These changes are indicative of distinct pathological mechanisms and may provide useful information to distinguish typical and atypical ON.     

Human Th17 cells

The discovery in mice of a new lineage of CD4⁺ effector T helper (Th) cells that selectively produce IL-17 has provided exciting new insights into immune regulation, host defence, and the pathogenesis of autoimmune and other chronic inflammatory disorders. This population of CD4⁺ Th cells, which has been termed 'Th17', indeed plays an apparently critical role in the pathogenesis of some murine models of autoimmunity. Interestingly, murine Th17 cells share a common origin with Foxp3⁺ T regulatory cells, because both populations are produced in response to transforming growth factor-β, but they develop into Th17 cells only when IL-6 is simultaneously produced. Initial studies in humans have confirmed the existence of Th17 cells, but they have shown that the origin of these cells in humans differs from that in mice, with IL-1β and IL-23 being the major cytokines responsible for their development. Moreover, the presence in the circulation and in various tissues of Th cells that can produce both IL-17 and interferon-γ, as well as the flexibility of human Th17 clones to produce interferon-γ in addition to IL-17 in response to IL-12, suggests that there may be a developmental relationship between Th17 and Th1 cells, at least in humans. Resolving this issue has great implications in tems of establishing the respective pathogenic roles of Th1 and Th17 cells in autoimmune disorders. In contrast, it is unlikely that Th17 cells contribute to the pathogenesis of human allergic IgE-mediated disorders, because IL-4 and IL-25 (a powerful inducer of IL-4) are both potent inhibitors of Th17 cell development.     

The generation of Th memory in neonates versus adults: prolonged primary Th2 effector function and impaired development of Th1 memory effector function in murine neonates

Immunization during the neonatal period often results in Th2-biased secondary responses. To understand the regulation of this phenomenon, we have examined all phases of Th development, from the generation of primary effectors to the duration of the primary effector stage to the production of memory effector function. First, we had previously reported that although primary responses in the neonatal lymph nodes are mature, mixed Th1/Th2-like, primary responses in the spleens of the same animals are exclusively Th2-like. To determine whether Th2-dominant secondary responses are due to the Th2-polarized primary function in the spleen, neonates were splenectomized before immunization. Even in the absence of primary neonatal splenic responses, the secondary responses of neonates were Th2 dominant. Thus, the overwhelmingly Th2 primary responses in the neonatal spleen are not required to generate Th2-dominant memory in the lymph nodes. Second, we have compared the kinetics of the primary response phase in neonates and adults. In adults, Ag-specific Th2 function disappeared rapidly from both the lymph nodes and spleen. In contrast, primary Th2 function persisted out to 5 wk in both neonatal organs. Third, the generation of Th memory responses was examined in animals initially immunized as neonates and in adults. These experiments demonstrated that neonates are selectively impaired in the development of Th1 memory effector function. Together, these results indicate that neonates are biased to Th2 function at all phases of an immune response.     

Th17 and Th22 cells in psoriatic arthritis and psoriasis

Introduction

The aim of this study was to characterize interleukin 17 (IL-17) and interleukin 22 (IL-22) producing cells in peripheral blood (PB), skin, synovial fluid (SF) and synovial tissue (ST) in patients with psoriasis (Ps) and psoriatic arthritis (PsA).

Methods

Flow cytometry was used to enumerate cells making IL-22 and IL-17, in skin and/or SF and PB from 11 patients with Ps and 12 patients with PsA; skin and PB of 15 healthy controls and SF from rheumatoid arthritis (RA) patients were used as controls. Expression of the interleukin 23 receptor (IL-23R) and chemokine receptors CCR4 and CCR6 was examined. Secretion of IL-17 and IL-22 was measured by ELISA. ST was analysed by immunohistochemical staining of IL-17 and IL-22.

Results

Increased frequencies of IL-17+ and IL-22+ CD4+ T cells were seen in PB of patients with PsA and Ps. IL-17 secretion was significantly elevated in both PsA and Ps, whilst IL-22 secretion was higher in PsA compared to Ps and healthy controls. A higher proportion of the CD4+ cells making IL-17 or IL-22 expressed IL-23R and frequencies of IL-17+, CCR6+ and CCR4+ T cells were elevated in patients with Ps and those with PsA. In patients with PsA, CCR6+ and IL-23R + T cells numbers were elevated in SF compared to PB. Increased frequencies of IL-17+ and IL-22+ CD4+ T cells were demonstrated in Ps skin lesions. In contrast, whilst elevated frequencies of CD4+ IL-17+ cells were seen in PsA SF compared to PB, frequencies of CD4+ IL-22+ T cells were lower. Whereas IL-17 expression was equivalent in PsA, osteoarthritis (OA) and RA ST, IL-22 expression was higher in RA than either OA or PsA ST, in which IL-22 was strikingly absent.

Conclusions

Elevated frequencies of IL-17 and IL-22 producing CD4+ T cells were a feature of both Ps and PsA. However their differing distribution at disease sites, including lower frequencies of IL-22+ CD4+ T cells in SF compared to skin and PB, and lack of IL-22 expression in ST suggests that Th17 and Th22 cells have common, as well as divergent roles in the pathogenesis of Ps and PsA.     

IL-17 and Th17 cells in human inflammatory diseases

IL-17 was discovered in 1995/96 as a T cell derived cytokine with effects on inflammation and neutrophil activation. In 2006, the precise cell source of IL-17 was identified in the mouse, and these cells were named Th17 cells. They play a role in various human diseases associated with inflammation and destruction such as rheumatoid arthritis, psoriasis, Crohn's disease, multiple sclerosis, where IL-17 can be seen as a therapeutic target.     

Difference in Th1 and Th17 lymphocyte adhesion to endothelium

T cell subset-specific migration to inflammatory sites is tightly regulated and involves interaction of the T cells with the endothelium. Th17 cells often appear at different inflammatory sites than Th1 cells, or both subsets appear at the same sites but at different times. Differences in T cell subset adhesion to endothelium may contribute to subset-specific migratory behavior, but this possibility has not been well studied. We examined the adhesion of mouse Th17 cells to endothelial adhesion molecules and endothelium under flow in vitro and to microvessels in vivo and we characterized their migratory phenotype by flow cytometry and quantitative RT-PCR. More Th17 than Th1 cells interacted with E-selectin. Fewer Th17 than Th1 cells bound to TNF-α-activated E-selectin-deficient endothelial cells, and intravital microscopy studies demonstrated that Th17 cells engage in more rolling interactions with TNF-α-treated microvessels than Th1 cells in wild-type mice but not in E-selectin-deficient mice. Th17 adhesion to ICAM-1 was dependent on integrin activation by CCL20, the ligand for CCR6, which is highly expressed by Th17 cells. In an air pouch model of inflammation, CCL20 triggered recruitment of Th17 but not Th1 cells. These data provide evidence that E-selectin- and ICAM-1-dependent adhesion of Th17 and Th1 cells with endothelium are quantitatively different.     

Elevated Frequencies of Circulating Th22 Cell in Addition to Th17 Cell and Th17/Th1 Cell in Patients with Acute Coronary Syndrome

Background

Atherosclerosis is a chronic inflammatory disease mediated by immune cells. Th22 cells are CD4⁺ T cells that secret IL-22 but not IL-17 or IFN-γ and are implicated in the pathogenesis of inflammatory disease. The roles of Th22 cells in the pathophysiologic procedures of acute coronary syndrome (ACS) remain unclear. The purpose of this study is to investigate the profile of Th22, Th17 and Th17/Th1 cells in ACS patients, including unstable angina (UA) and acute myocardial infarction (AMI) patients.

Design and Methods

In this study, 26 AMI patients, 16 UA patients, 16 stable angina (SA) patients and 16 healthy controls were included. The frequencies of Th22, Th17 and Th17/Th1 cells in AMI, UA, SA patients and healthy controls were examined by flow cytometry. Plasma levels of IL-22, IL-17 and IFN-γ were measured by enzyme-linked immunosorbent assay (ELISA).

Results

Th22, Th17 and Th17/Th1 cells were significantly increased in AMI and UA patients compared with SA patients and healthy controls. Moreover, plasma IL-22 level was significantly elevated in AMI and UA patients. In addition, Th22 cells correlated positively with IL-22 as well as Th17 cells in AMI and UA patients.

Conclusion

Our findings showed increased frequencies of both Th22 and Th17 cells in ACS patients, which suggest that Th22 and Th17 cells may play a potential role in plaque destabilization and the development of ACS.