Inhibition of Th17 cells regulates autoimmune diabetes in NOD mice

Therapeutic potential of anti-interleukin-17A aptamer: suppression of interleukin-17A signaling and attenuation of autoimmunity in two mouse models

OBJECTIVE

The proinflammatory cytokine interleukin-17A (IL-17A) is produced primarily by the CD4+ T cell subset called Th17 cells, which is involved in host defense, inflammation, and autoimmune disorders. This study was undertaken to investigate the effect of a high-affinity RNA molecule, called an aptamer, against human IL-17A on IL-17A-induced signal transduction in vitro and its anti-autoimmune efficacy in vivo in 2 mouse models of inflammation.

METHODS

By screening a large library of nuclease-resistant RNA oligonucleotides, we selected an RNA aptamer, Apt21-2, that binds human and mouse IL-17 and blocks the interaction between IL-17A and its receptor. The inhibition of IL-17A-mediated phosphorylation and marker protein production was analyzed in human and mouse cells. Mice with glucose-6-phosphate isomerase (GPI)-induced rheumatoid arthritis and myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis were used to assess efficacy.

RESULTS

Apt21-2 prevented efficient phosphorylation of the IL-17A signaling factors IκB and JNK and inhibited the production of IL-6 in human and mouse cells. A PEGylated form of Apt21-2 (PEG21-2idT) exhibited a 50% inhibition concentration (IC(50) ) in the range of 1-2 nM and 70-80 nM in human and mouse cells, respectively. When administered immediately after immunization with GPI or MOG, PEG21-2idT inhibited in a dose-dependent manner the development of arthritic or neurologic symptoms. Significantly, PEG21-2idT slowed the progression of arthritis when administered after the onset of GPI-induced arthritis.

CONCLUSION

Our findings indicate that the chemically processed anti-IL-17A aptamer PEG21-2idT inhibits the actions of IL-17A as well as the development of autoimmunity in 2 mouse models of inflammation. These results offer for the first time an aptamer-based therapeutic approach to the treatment of Th17 cell-mediated autoimmune disorders.

HE3286, an orally bioavailable synthetic analogue of an active DHEA metabolite suppresses spontaneous autoimmune diabetes in the non-obese diabetic (NOD) mouse

5-Androstene-3β,7β,17β-triol (AET) is a naturally occurring anti-inflammatory adrenal steroid that limits acute and chronic inflammation. HE3286 (17α-ethynyl-5-androstene-3β,7β,17β-triol) is a synthetic derivative of AET with improved pharmaceutical properties and efficacy in some animal models of autoimmunity. Here, daily oral doses of HE3286 led to a suppression of spontaneous autoimmune diabetes in the non-obese diabetic mouse model of type 1 diabetes mellitus when administered either shortly before or after the first incidence of disease onset. Efficacy was associated with reduced insulitis and a suppression of the pathogenic T helper cell type 1 and type 17 phenotypes in peripheral lymphoid organs. These results demonstrate that daily oral treatment with HE3286 administrated relatively late in the destructive autoimmune process led to a suppression of type 1 diabetes mellitus onset and of the pathological inflammatory status, supporting its clinical evaluation in type 1 diabetes mellitus subjects.

Cytokine and autoantibody patterns in acute liver failure

The mechanisms of idiosyncratic drug-induced liver injury (IDILI) are still a matter of dispute. Some of the characteristics of reactions that have been classed as metabolic idiosyncrasy could also be those of an immune-mediated reaction with an autoimmune component. Many auto-immune reactions appear to be mediated by T(H)17 cells, which are in part characterized by the production of interleukin (IL)-17. To test the involvement of T(H)17 cells in IDILI, we quantified a number of cytokines, chemokines, and autoantibodies in the serum of 39 patients with acute liver failure (ALF) due to IDILI and compared the values with those from 21 patients with acetaminophen-induced ALF and 10 patients with viral hepatitis-induced ALF. The IL-17 levels were elevated in 60% of patients with IDILI, but also in a similar number of patients with acetaminophen-induced ALF and occasionally in patients with viral hepatitis. Levels of other cytokines, such as IL-21, that are also produced by T(H)17 cells were higher in patients with IDILI, but again, there was overlap with acetaminophen DILI. Autoantibodies were more frequent in patients in the IDILI group but were absent in most patients. These data provide a picture of the cytokine/chemokine profile in patients with various types of ALF. The pattern varies from patient to patient and not specifically by etiology. This suggests that different underlying disease mechanisms may be at play in different individuals, even among those demonstrating injury from the same drug. Since cytokines may originate from more than one type of cell, interpretation of results of cytokine assays remains difficult in complex disease settings.

Hypertension in response to placental ischemia during pregnancy: role of B lymphocytes

Preeclampsia is associated with innate inflammatory response resulting in elevated tumor necrosis factor-α, agonistic autoantibodies to the angiotensin II type I receptor, and activation of endothelin 1 (ET-1). This study was designed to determine the role of B-cell depletion, resulting in agonistic autoantibodies to the angiotensin II type I receptor suppression to mediate hypertension via activation of ET-1 in the placental ischemic reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. To achieve this goal we examined the effect of RUPP on mean arterial pressure and ET-1 in the presence and absence of chronically infused rituximab (R; 250 mg/kg), a B-lymphocyte-suppressive agent used clinically to treat autoimmune diseases. Mean arterial pressure was 103±1 mm Hg in normal pregnant (NP) rats; 103±3 mm Hg in NP+R versus 133±2 mm Hg in RUPP rats, and 118±2 mm Hg in RUPP+R rats (P<0.001 vs RUPP controls). B lymphocytes decreased from 6.0±0.5% gated cells in RUPP to 3.7±0.8% gated cells in RUPP+R rats. Importantly, agonistic autoantibodies to the angiotensin II type I receptor decreased from 18±1 bpm in RUPP rats to 10±1 bpm in RUPP+R rats. ET-1 decreased 1.5-fold in kidneys and 4-fold in the placenta (P<0.01) of RUPP+R versus RUPP rats. Media ET-1 excretion from endothelial cells exposed to serum from NP, RUPP, NP+R, or RUPP+R rats was determined. ET-1 from endothelial cells treated with NP serum was 53+13 pg/mg and increased to 75+10 pg/mg with RUPP serum. In contrast, ET-1 secretion decreased in response to B-cell-depleted RUPP serum to 50±8 pg/mg and was unchanged in response to NP+R sera (46±12 pg/mg). These data demonstrate the important roles that B-lymphocyte activation and agonistic autoantibodies to the angiotensin II type I receptors play in the pathophysiology of hypertension in response to placental ischemia.

Functional specialization of interleukin-17 family members

Interleukin-17A (IL-17A) is the signature cytokine of the recently identified T helper 17 (Th17) cell subset. IL-17 has six family members (IL-17A to IL-17F). Although IL-17A and IL-17F share the highest amino acid sequence homology, they perform distinct functions; IL-17A is involved in the development of autoimmunity, inflammation, and tumors, and also plays important roles in the host defenses against bacterial and fungal infections, whereas IL-17F is mainly involved in mucosal host defense mechanisms. IL-17E (IL-25) is an amplifier of Th2 immune responses. The functions of IL-17B, IL-17C, and IL-17D remain largely elusive. In this review, we describe the identified functions of each IL-17 family member and discuss the potential of these molecules as therapeutic targets.

Structure and function of interleukin-17 family cytokines

The recently identified interleukin-17 (IL-17) cytokines family, which comprises six members in mammals (IL-17A-F), plays essential roles in the host immunity against infectious diseases and chronic inflammatory diseases. The three-dimensional structures containing IL-17A or IL-17F have become available and revealed the unique structural features of IL-17s as well as their receptors. Molecular modeling in this review shows that IL-17s may adopt a "cysteine knot" fold commonly seen in nerve growth factor (NGF) and other neurotrophins. Further modeling analysis unmasks a signature interaction feature of the IL-17F/IL-17RA complex, where a small loop of IL-17RA slots into the deep groove of the interface of IL-17F homodimer. This is quite different from the interaction between the best known four-helix cytokines and their cognate receptors. On the other hand, structure of IL-17A and its monoclonal antibody (CAT-2200) shows that, albeit that the antigenic epitope of IL-17A resides outside of the IL-17A homodimer interface, its physical proximity to the receptor binding groove may explain that antibody blockage would be achieved by interfering with the ligand-receptor interaction. This review is to summarize the advance in understanding the structure and function of IL-17 family cytokines, focusing mainly on IL-17A, IL-17F and IL-17E, in the hope of gaining better knowledge of immunotherapeutic strategies against various inflammatory diseases.

Interleukin-1β produced in response to islet autoantigen presentation differentiates T-helper 17 cells at the expense of regulatory T-cells: Implications for the timing of tolerizing immunotherapy

OBJECTIVE

The effectiveness of tolerizing immunotherapeutic strategies, such as anti-CD40L or dendritic cells (DCs), is greater when administered to young nonobese diabetic (NOD) mice than at peak insulitis. RelB(lo) DCs, generated in the presence of an nuclear factor-κB inhibitor, induce T-regulatory (Treg) cells and suppress inflammation in a model of rheumatoid arthritis. Interleukin (IL)-1β is overexpressed in humans and mice at risk of type 1 diabetes, dysregulates Treg cells, and accelerates diabetes in NOD mice. We investigated the relationship between IL-1β production and the response to RelB(lo) DCs in the prediabetic period.

RESEARCH DESIGN AND METHODS

We injected RelB(lo) DCs subcutaneously into 4- or 14-week-old NOD mice and tracked the incidence of diabetes and effect on Treg cell function. We measured the expression of proinflammatory cytokines by stimulated splenocytes and unstimulated islets from mice of different ages and strains and proliferative and cytokine responses of T effectors to Treg in vitro.

RESULTS

Tolerizing RelB(lo) DCs significantly inhibited diabetes progression when administered to 4-week-old but not 14-week-old mice. IL-1β production by NOD splenocytes and mRNA expression by islets increased from 6 to 16 weeks of age when major histocompatibility complex (MHC)-restricted islet antigen presentation to autoreactive T-cells occurred. IL-1 reduced the capacity of Treg cells to suppress effector cells and promoted their conversion to Th17 cells. RelB(lo) DCs exacerbated the IL-1-dependent decline in Treg function and promoted Th17 conversion.

CONCLUSIONS

IL-1β, generated by islet-autoreactive cells in MHC-susceptible mice, accelerates diabetes by differentiating Th17 at the expense of Treg. Tolerizing DC therapies can regulate islet autoantigen priming and prevent diabetes, but progression past the IL-1β/IL-17 checkpoint signals the need for other strategies.

Taenia crassiceps infection abrogates experimental autoimmune encephalomyelitis

Helminth infections induce strong immunoregulation that can modulate subsequent pathogenic challenges. Taenia crassiceps causes a chronic infection that induces a Th2-biased response and modulates the host cellular immune response, including reduced lymphoproliferation in response to mitogens, impaired antigen presentation and the recruitment of suppressive alternatively activated macrophages (AAMФ). In this study, we aimed to evaluate the ability of T. crassiceps to reduce the severity of experimental autoimmune encephalomyelitis (EAE). Only 50% of T. crassiceps-infected mice displayed EAE symptoms, which were significantly less severe than uninfected mice. This effect was associated with both decreased MOG-specific splenocyte proliferation and IL-17 production and limited leukocyte infiltration into the spinal cord. Infection with T. crassiceps induced an anti-inflammatory cytokine microenvironment, including decreased TNF-α production and high MOG-specific production of IL-4 and IL-10. While the mRNA expression of TNF-α and iNOS was lower in the brain of T. crassiceps-infected mice with EAE, markers for AAMФ were highly expressed. Furthermore, in these mice, there was reduced entry of CD3(+)Foxp3(-) cells into the brain. The T. crassiceps-induced immune regulation decreased EAE severity by dampening T cell activation, proliferation and migration to the CNS.

Aberrant ROCK activation promotes the development of type I diabetes in NOD mice

Aberrant production of IL-21 by T cells is critical for the development of type 1 diabetes (T1D) in NOD mice. The pathogenic effects of IL-21 are partly due to its ability to promote the generation of T(H)-17 cells. Interferon Regulatory Factor (IRF4) is a crucial regulator of IL-17 and IL-21 production. We recently found that the serine-threonine kinase ROCK2 phosphorylates IRF4 and regulates its ability to control IL-17 and IL-21 production. Here we show that NOD T cells aberrantly activate ROCK2. We furthermore demonstrate that ROCK inhibition corrects the abnormal IRF4 function in NOD T cells and diminishes their production of IL-17 and IL-21. Importantly, administration of a ROCK inhibitor to NOD mice protects against diabetes development. These studies thus support the idea that ROCK2 is inappropriately activated in NOD T cells and that ROCK kinases could represent important therapeutic targets for the treatment of T1D.

Detecting rejection after mouse Islet transplantation utilizing islet protein-stimulated ELISPOT

Improved posttransplant monitoring and on-time detection of rejection could improve islet transplantation outcome. The present study explored the possibility of detecting harmful events after mouse islet transplantation measuring the immune responsiveness against islet extracts. Mouse islet transplantations were performed using various donor/recipient combinations, exploring autoimmune (NOD/SCID to NOD, n = 6) and alloimmune events (C57BL/6 to BALB/c, n = 20), a combination of both (C57BL/6 to NOD, n = 8), the absence of both (BALB/c to BALB/c, n = 21), or naive, nontransplanted control mice (n = 14). The immune reactivity was measured by ELISPOT, looking at the ex vivo release of IFN-γ from splenocytes stimulated by islet donor extracts (sonicated islets). The immune reactivity was not altered in the syngeneic and autoimmune models, demonstrating similar levels as nontransplanted controls (p = 0.46 and p = 0.6). Conversely, the occurrence of an allogeneic rejection alone or in combination to autoimmunity was associated to an increase in the level of immune reactivity (p = 0.023 and p = 0.003 vs. respective controls). The observed increase was transient and lost in the postrejection period or after treatment with CTLA4-Ig. Overall, allogeneic rejection was associated to a transient increase in the reactivity of splenocytes against islet proteins. Such a strategy has the potential to improve islet graft monitoring in human and should be further explored.

The presence of IL-17A and T helper 17 cells in experimental mouse brain tumors and human glioma

Background

Recently, CD4⁺IL-17A⁺ T helper 17 (Th17) cells were identified and reported in several diseased states, including autoimmunity, infection and various peripheral nervous system tumors. However, the presence of Th17 in glia-derived tumors of the central nervous system has not been studied.

Methodology/Principal Findings

In this report, we demonstrate that mRNA expression for the Th17 cell cytokine IL-17A, as well as Th17 cells, are present in human glioma. The mRNA expression for IL-17A in glioma was recapitulated in an immunocompetent mouse model of malignant glioma. Furthermore, the presence of Th17 cells was confirmed in both human and mouse glioma. Interestingly, some Th17 cells present in mouse glioma co-expressed the Th1 and Th2 lineage markers, IFN-γ and IL-4, respectively, but predominantly co-expressed the Treg lineage marker FoxP3.

Conclusions

These data confirm the presence of Th17 cells in glia-derived CNS tumors and provide the rationale for further investigation into the role of Th17 cells in malignant glioma.

Inflammatory tendencies and overproduction of IL-17 in the colon of young NOD mice are counteracted with diet change

OBJECTIVE

Dietary factors influence diabetes development in the NOD mouse. Diet affects the composition of microbiota in the distal intestine, which may subsequently influence intestinal immune homeostasis. However, the specific effects of antidiabetogenic diets on gut immunity and the explicit associations between intestinal immune disruption and type 1 diabetes onset remain unclear.

RESEARCH DESIGN AND METHODS

Gut microbiota of NOD mice fed a conventional diet or ProSobee formula were compared using gas chromatography. Colonic lamina propria immune cells were characterized in terms of activation markers, cytokine mRNA and Th17 and Foxp3(+) T-cell numbers, using real-time PCR and flow cytometry. Activation of diabetogenic CD4 T-cells by purified B-cells was assessed in both groups. Immune tolerance to autologous commensal bacteria was evaluated in vitro using thymidine-incorporation tests.

RESULTS

Young NOD mice showed a disturbed tolerance to autologous commensal bacteria. Increased numbers of activated CD4 T-cells and (CD11b(+)CD11c(+)) dendritic cells and elevated levels of Th17 cells and IL23 mRNA were moreover observed in colon lamina propria. These phenomena were abolished when mice were fed an antidiabetogenic diet. The antidiabetogenic diet also altered the expression levels of costimulatory molecules and the capacity of peritoneal B-cells to induce insulin-specific CD4 T-cell proliferation.

CONCLUSIONS

Young NOD mice show signs of subclinical colitis, but the symptoms are alleviated by a diet change to an antidiabetogenic diet. Disrupted immune tolerance in the distal intestine may influence peritoneal cell pools and B-cell-mediated activation of diabetogenic T-cells.

Cutting edge: Increased IL-17-secreting T cells in children with new-onset type 1 diabetes

CD4(+)FOXP3(+) regulatory T cells are essential for immune tolerance, and murine studies suggest that their dysfunction can lead to type 1 diabetes (T1D). Human studies assessing regulatory T cell dysfunction in T1D have relied on analysis of FOXP3-expressing cells. Recently, distinct subsets of CD4(+)FOXP3(+) T cells with differing function were identified. Notably, CD45RA(-)CD25(int)FOXP3(low) T cells lack suppressive function and secrete the proinflammatory cytokine IL-17. Therefore, we evaluated whether the relative fractions of CD4(+)FOXP3(+) subsets are altered in new-onset T1D subjects. We report that children with new-onset T1D have an increased proportion of CD45RA(-)CD25(int)FOXP3(low) cells that are not suppressive and secrete significantly more IL-17 than other FOXP3(+) subsets. Moreover, these T1D subjects had a higher proportion of both CD4(+) and CD8(+) T cells that secrete IL-17. The bias toward IL-17-secreting T cells in T1D suggests a role for this proinflammatory cytokine in the pathogenesis of disease.

Neutralization of IL-9 ameliorates experimental autoimmune encephalomyelitis by decreasing the effector T cell population

Multiple sclerosis is a CD4(+) T cell-mediated autoimmune disease affecting the CNS. Multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), have been thought to be Th1-mediated diseases. However, recent studies provide strong evidence that the major pathogenic T cell subsets in EAE are Th17 cells. IL-9, a hematopoietic growth factor, is considered to be a mediator of Th17 cells, but the precise mechanisms of its action are largely unknown. The present study was designed to investigate the role of IL-9 in autoimmune demyelination. IL-9 blockade with anti-IL-9 mAb inhibited the development of EAE, reduced the serum levels of IL-17, the CNS mRNA expression of IL-17, IL-6, IFN-γ, and TNF-α, and the myelin oligodendrocyte glycoprotein (MOG)-induced IL-17, IFN-γ secretion of lymphocytes. Furthermore, anti-IL-9 mAb in culture suppressed IL-17 production of MOG-reactive T cells and their potency in adoptive transfer EAE. These findings indicate that the protective effect of IL-9 blockade in EAE was likely mediated via inhibition of the development of MOG peptide-specific T cells, which in turn led to reduced infiltration of T cells into the CNS. Thus, anti-IL-9 mAb treatment may provide an effective therapeutic strategy against autoimmune diseases.

Complement-mediated regulation of the IL-17A axis is a central genetic determinant of the severity of experimental allergic asthma

Severe asthma is associated with the production of interleukin 17A (IL-17A). The exact role of IL-17A in severe asthma and the factors that drive its production are unknown. Here we demonstrate that IL-17A mediated severe airway hyperresponsiveness (AHR) in susceptible strains of mice by enhancing IL-13-driven responses. Mechanistically, we demonstrate that IL-17A and AHR were regulated by allergen-driven production of anaphylatoxins, as mouse strains deficient in complement factor 5 (C5) or the complement receptor C5aR mounted robust IL-17A responses, whereas mice deficient in C3aR had fewer IL-17-producing helper T cells (T(H)17 cells) and less AHR after allergen challenge. The opposing effects of C3a and C5a were mediated through their reciprocal regulation of IL-23 production. These data demonstrate a critical role for complement-mediated regulation of the IL-23-T(H)17 axis in severe asthma.

Gut-residing segmented filamentous bacteria drive autoimmune arthritis via T helper 17 cells

Commensal microbes can have a substantial impact on autoimmune disorders, but the underlying molecular and cellular mechanisms remain largely unexplored. We report that autoimmune arthritis was strongly attenuated in the K/BxN mouse model under germ-free (GF) conditions, accompanied by reductions in serum autoantibody titers, splenic autoantibody-secreting cells, germinal centers, and the splenic T helper 17 (Th17) cell population. Neutralization of interleukin-17 prevented arthritis development in specific-pathogen-free K/BxN mice resulting from a direct effect of this cytokine on B cells to inhibit germinal center formation. The systemic deficiencies of the GF animals reflected a loss of Th17 cells from the small intestinal lamina propria. Introduction of a single gut-residing species, segmented filamentous bacteria, into GF animals reinstated the lamina propria Th17 cell compartment and production of autoantibodies, and arthritis rapidly ensued. Thus, a single commensal microbe, via its ability to promote a specific Th cell subset, can drive an autoimmune disease.

IL-17 immunity in human type 1 diabetes

Th17 immunity has been shown to regulate autoimmune diabetes in mice. IL-17 neutralization prevented development of diabetes when given postinitiation of insulitis but not earlier, suggesting interference with the effector phase of the disease. Islet-cell Ag-specific Th17 cells converted into IFN-gamma-secreting Th1-like cells and caused diabetes in mice recipients. The role of IL-17 in human type 1 diabetes (T1D) is, however, not established. In this study, we show upregulation of Th17 immunity in peripheral blood T cells from children with T1D. This was characterized by increased IL-17 secretion and expression of IL-17, IL-22, and retinoic acid-related orphan receptor C isoform 2, but also FOXP3 transcripts upon T cell activation in vitro. Also, circulating memory CD4 cells from children with T1D showed the same pattern of IL-17, IL-22 and FOXP3 mRNA upregulation, indicating IL-17 pathway activation in vivo. IL-17-positive T cells appeared to be CD4(+) cells expressing TCR-alphabeta and CCR6, and a subpopulation showed coproduction of IFN-gamma. Given the Th17 immunity in T1D, we demonstrated that IL-17 had detrimental effects on human islet cells in vitro; it potentiated both inflammatory and proapoptotic responses. Our findings highlight the role of IL-17 immunity in the pathogenesis of human T1D and point to a potential therapeutic strategy.

Type 1 diabetes in BioBreeding rats is critically linked to an imbalance between Th17 and regulatory T cells and an altered TCR repertoire

Diabetes-prone BioBreeding (DP-BB) rats spontaneously develop type 1 diabetes mellitus (T1DM) on grounds of their MHC haplotype RT1(u) and a point mutation in the Gimap5 gene. In this study, we report that DP-BB rats exhibit an increasingly severe imbalance, in particular between Th17 and regulatory T (T(reg)) cells, within the first months of age. This can be assigned to an excess in effector T cells because neither the percentage nor the function of the T(reg) cells is compromised. Flow cytometric analysis of Vbeta segment usage and CDR3 spectratyping further suggest that the disturbed repertoire of peripheral T cells may also contribute to the development of T1DM in DP-BB rats. Importantly, expansion of T(reg) cells in vivo by means of a CD28 superagonistic Ab as well as adoptive transfer of T(reg) cells efficiently interferes with the development of T1DM in DP-BB rats, whereas treatment with conventional Th cells does not afford protection. Using a newly generated strain of enhanced GFP transgenic rats, we could further demonstrate that the transferred T(reg) cells persist in the recipient rats for several months and partially correct the imbalance between Th17 and T(reg) cells. Thus, our data support the hypothesis that unchecked effector T cell action and a disturbed T cell repertoire contribute to the development of T1DM in DP-BB rats, which may also have implications for a better understanding of the human disease.

Interleukin-17-producing T helper cells in autoimmunity

With all the incredible progress in scientific research over the past two decades, the trigger of the majority of autoimmune disorders remains largely elusive. Research on the biology of T helper type 17 (T(H)17) cells over the last decade not only clarified previous observations of immune regulations and disease manifestations, but also provided considerable information on the signaling pathways mediating the effects of this lineage and its seemingly dual role in fighting the invading pathogens on one hand, and in frightening the host by inducing chronic inflammation and autoimmunity on the other hand. In this context, recent reports have implicated T(H)17 cells in mediating host defense as well as a growing list of autoimmune diseases in genetically-susceptible individuals. Herein, we summarize the current knowledge on T(H)17 in autoimmunity with emphasis on its differentiation factors and some mechanisms involved in initiating pathological events of autoimmunity.

Th 17 cells interplay with Foxp3+ Tregs in regulation of inflammation and autoimmunity

T helper 17 cells (Th17) are a new CD4+ T helper subset that has been implicated in inflammatory and autoimmune diseases. Th17, along with CD4(+)CD25(high) Foxp3(+) regulatory T cells (Tregs) and other new T helper subsets, have expanded the Th1-Th2 paradigm. Although this new eight-subset paradigm significantly improved our understanding on the differentiation and regulation of CD4+ T helper subsets, many questions remain to be answered. Here we will briefly review the following issues: a) Old Th1-Th2 paradigm versus new multi-subset paradigm; b) Structural features of IL-17 family cytokines; c) Th17 cells; d) Effects of IL-17 on various cell types and tissues; e) IL-17 receptor and signaling pathways; f) Th17-mediated inflammations; and g) Protective mechanisms of IL-17 in infections. Lastly, we will examine the interactions of Th17 and Treg in autoimmune diseases and inflammation: Th17 cells interplay with Tregs. Regulation of autoimmunity and inflammation lies in the interplays of the different T helper subsets, therefore, better understanding of these subsets' interactions would greatly improve our approaches in developing therapy to combat inflammatory and autoimmune diseases.

Transfusion of nonobese diabetic mice with allogeneic newborn blood ameliorates autoimmune diabetes and modifies the expression of selected immune response genes

Although allogeneic bone marrow transplantation has been shown to prevent autoimmune diabetes in heavily irradiated nonobese diabetic (NOD) mice, a similar procedure is not suitable for the treatment of patients with type 1 diabetes because of associated severe side effects. Therefore, we evaluated whether mouse newborn blood (NBB), equivalent to human umbilical cord blood, could be used for diabetes prevention without recipient preconditioning. To test this hypothesis, unconditioned, prediabetic female NOD mice were given a single injection of whole NBB derived from the allogeneic diabetes-resistant mouse strain C57BL/6. Transfusion of allogeneic NBB but not adult blood prevented diabetes incidence in a majority of treated mice for a prolonged period of time. This was accompanied by the release of insulin in response to a challenge with glucose. Invasive cellular infiltration of islets was also substantially reduced in these mice. Although NBB transfusion induced a low level of hematopoietic microchimerism, it did not strictly correlate with amelioration of diabetes. Induction of genes implicated in diabetes, such as Il18, Tnfa, and Inos but not Il4, Il17 or Ifng, was repressed in splenocytes derived from protected mice. Notably, expression of the transcription factor Tbet/Tbx21 but not Gata3 or Rorgt was upregulated in protected mice. These data indicate that allogeneic NBB transfusion can prevent diabetes in NOD mice associated with modulation of selected cytokine genes implicated in diabetes manifestation. The data presented in this study provide the proof of principle for the utility of allogeneic umbilical cord blood transfusion to treat patients with autoimmune diabetes.

Dried leaf extract of Olea europaea ameliorates islet-directed autoimmunity in mice

The health-promoting effects of various constituents of the olive tree (Olea europaea) are mainly associated with hypoglycaemic and insulin-sensitising activities and have been widely demonstrated in the metabolic syndrome and type 2 diabetes. However, their biological activity in autoimmune type 1 diabetes (T1D) is poorly characterised. Therefore, the influence of O. europaea-derived components present in dry olive leaf extract (DOLE) was examined in two established preclinical models of human T1D, which differ in some aspects of diabetogenesis: multiple low-dose streptozotocin-induced diabetes in susceptible C57BL/6 and CBA/H mouse strains; cyclophosphamide-accelerated diabetes in non-obese diabetic mice. In both T1D models, in vivo administration of DOLE significantly reduced clinical signs of diabetes (hyperglycaemia and body weight loss) and led to complete suppression of histopathological changes in pancreatic islets. In line with these, insulin expression and release were restored in DOLE-treated mice. Interestingly, inducible NO synthase expression and NO production were significantly elevated in peripheral tissues but were down-regulated within the local environment of the endocrine pancreas. This interference was reflected in NO-mediated suppression of T lymphocyte proliferation and lower production of the proinflammatory cytokines interferon-gamma, IL-17 and TNF-alpha in the spleen, with subsequent blockade of beta-cell destruction. The results suggest that DOLE interferes with development of autoimmune diabetes by down-regulating production of proinflammatory and cytotoxic mediators. Therefore, the potential use of a DOLE-enriched diet for prophylaxis/treatment of human T1D, and possibly other autoimmune diseases, is worthy of further investigation.

Fms-like tyrosine kinase 3 ligand decreases T helper type 17 cells and suppressors of cytokine signaling proteins in the lung of house dust mite-sensitized and -challenged mice

We previously reported that Fms-like tyrosine kinase 3 ligand (Flt3-L) reversed airway hyperresponsiveness (AHR) and airway inflammation, and increased the number of regulatory CD11c(high)CD8α(high)CD11b(low) dendritic cells and CD4(+)CD25(+)ICOS(+)Foxp3(+)IL-10(+) T-regulatory cells in the lung of allergen-sensitized and -challenged mice. In this study, we evaluated the effect of Flt3-L on Th17 cells and expression of suppressors of cytokine signaling (SOCS) proteins in the lungs of house dust mite (HDM)-sensitized and -challenged mice. BALB/c mice were sensitized and challenged with HDM, and AHR to methacholine was established. Mice were treated with Flt3-L (5 μg, intraperitoneal) daily for 10 days. Levels of IL-4, -5, -6, -8, and -13, and transforming growth factor (TGF)-β in the bronchoalveolar lavage fluid (BALF) were examined by ELISA. Flt3-L treatment reversed existing AHR to methacholine and substantially decreased eosinophils, neutrophils, IL-5, -6, -8, and IL-13, and TGF-β levels in the BALF. HDM-sensitized and -challenged mice showed a significant increase in lung CD4(+)IL-17(+)IL-23R(+)CD25⁻ T cells with high expression of retinoic acid-related orphan receptor (ROR)-γt transcripts. However, administration of Flt3-L substantially decreased the number of lung CD4(+)IL-17(+)IL-23R(+)CD25⁻ T cells, with significantly decreased expression of ROR-γt mRNA in these cells. HDM sensitization caused a significant increase in the expression of SOCS-1, -3, and -5 in the lung. Flt3-L treatment abolished the increase in SOCS-1 and SOCS-3 proteins, whereas SOCS-5 expression was significantly reduced. These data suggest that the therapeutic effect of Flt3-L in reversing the hallmarks of allergic asthma in a mouse model is mediated by decreasing IL-6 and TGF-β levels in the BALF, which, in turn, decrease CD4(+)IL-17(+)IL-23R(+)ROR-γt(+)CD25⁻ T cells and the expression of SOCS-1 and SOCS-3 in the lung of HDM-sensitized and -challenged mice.