Producing Th1 Cells Research Articles

Glycogen synthase kinase-3 is an early determinant in the differentiation of pathogenic Th17 cells. (152.3)

Abstract CD4+ T cells are critical for host defense but also drive immune-mediated diseases. The classical view of Th1 and Th2 subtypes of CD4+ T cells was recently revised by the identification of the Th17 lineage that produces IL-17 and are critical in autoimmune disease pathogenesis. Mechanisms controlling the differentiation of Th17 cells have been described, but few feasible targets for therapeutically reducing Th17 cells are known. The generation of Th17 cells requires IL-6 and activation of STAT3. During polarization of CD4+ T cells to Th17 cells, we found that inhibition of glycogen synthase kinase-3 (GSK3) blocked IL-6 production, STAT3 activation, and polarization to Th17 cells. Polarization of CD4+ T cells to Th17 cells increased by 10-fold GSK3β protein levels in Th17 cells, while GSK3β was unaltered in Treg cells. Diminishing GSK3 activity pharmacologically or molecularly blocked Th17 cell production, and increasing GSK3 activity promoted polarization to Th17 cells. In vivo inhibition of GSK3 in mice depleted constitutive Th17 cells in intestinal mucosa, blocked Th17 cell generation in the lung following Francisella tularensis infection, and inhibited the increase in spinal cord Th17 cells and disease symptoms in the experimental autoimmune encephalomyelitis (EAE) mouse MS model. These findings identify GSK3 as a critical mediator of Th17 cell production, and indicate that GSK3 inhibitors provide a potential therapeutic intervention to control Th17-mediated diseases.

Immunoproteasome activity controls the balance of inflammatory and regulatory gene expression in T helper cells (152.21)

Abstract The immunoproteasome (iPr), a unique form of the proteasome found in cells of the immune system, regulates cytokine production and differentiation of Th1 and Th17 cells in vitro in an NF-kB independent manner. However, the role of the iPr in other T-cell subsets and the specific molecular signaling events regulated by the iPr are not well understood. We found that FoxP3 and TGF-β expression increased in Treg cells exposed to a selective iPr inhibitor (ONX 0914, formerly PR-957) but that IL-4 production in Th2 cells was unaffected by iPr inhibition. Interestingly, increased FoxP3 expression was noted in Th0 and Th1 cells exposed to ONX 0914. Inhibition of the iPr resulted in reduced phosphorylation of STAT1 and STAT3 in Th1 and Th17 cells, respectively. Decreased basal and IL-6 stimulated STAT3 phosphorylation was noted immediately following iPr inhibition suggesting a receptor proximal event but at later timepoints coincided with reduced gene expression. After a brief exposure to ONX 0914, Th17 and Treg cells show a similar pattern of protein accumulation as measured by 2D Diffference Gel Electrophoresis and included the regulatory subunit of PP2A, a protein phosphatase known to regulate STAT3 and other transcription factors. Collectively, these results suggest that the iPr regulates Th cell plasticity via PP2A activity.

Immune dampening at the source

Two U.S. academic groups have identified RAR-related orphan receptor inhibitors that block production of proinflammatory Th17 cells and decrease the severity of multiple sclerosis in mice. Independently, Merck and biotech partner Lycera are targeting one of these receptors for RA, psoriasis and other autoimmune diseases.

Role of novel microRNAs in immunological dysfunction associated with PTSD (117.13)

Abstract The immunological dysfunction in combat veterans with post-traumatic stress disorder (PTSD) has not been understood. The current study aimed to evaluate the role of novel microRNAs (miRNAs) in immunological dysfunction associated with PTSD. Our studies demonstrated that both PBMC and CD4+ T cells in peripheral blood significantly increased in PTSD patients as compared with controls. Further studies showed that the percentage of IFN-γ producing Th1 cells was much higher in PTSD patients than normal donors. Multiple cytokine assays indicated that PBMC from PTSD patients produced more IL-1β, IL-2, IL-17, G-CSF and IFN-γ than those from controls. Our results demonstrate that PTSD is associated with proinflammatory response. High-throughput miRNA array hybridization analysis showed that several novel miRNAs such as miR-664 and miR-1291were significantly up-regulated, whereas miR-125a and miR-181c were dramatically down-regulated in PTSD patients. Real-time PCR confirmed that several of these miRNAs such as miR-125a and miR-181c significantly decreased in PTSD patients. Our further studies demonstrated that down-regulation of miR-125a may be responsible for increased IFN-γ production in PTSD patients. The results suggest that some novel miRNAs may play a role in immunological dysfunction associated with PTSD and such novel miRNAs may be used as biomarkers for diagnosis or as a therapeutic remedy for PTSD.

Trp53 negatively regulates autoimmunity via the STAT3-Th17 axis (167.27)

Abstract Emerging evidence suggests that the tumor suppressor p53 is also a crucial regulatory factor for many physiological processes. Previous observations indicate that p53 negatively regulates inflammation via suppressing inflammatory cytokine production by antigen presenting cells. However, the role of p53 in regulating autoimmune effector T cells, such as IL-17 producing Th17 cells, is largely unknown. Here, we demonstrate that p53nullCD45.1 mice spontaneously develop autoimmunity associated with a significant increase in Th17 cells in their lymphoid and pathological tissues as well as elevated levels of inflammatory cytokines IL-6 and IL-17 in serum. This increase in Th17 response results largely from an increased sensitivity of p53nullCD45.1 T cells to IL-6 induced STAT3 phosphorylation. Administration of a STAT3 inhibitor to p53nullCD45.1 mice reduced the frequency of Th17 cells and alleviated autoimmune pathology. This is the first report, to our knowledge, revealing the contribution of T-cell p53 in the suppression of autoimmunity by controlling Th17 differentiation. This study suggests that p53 serves as a guardian of proper immunological functions and that the p53-STAT3-Th17 axis might be a therapeutic target for autoimmunity.

Interleukin 17 increases blood pressure during pregnancy: a link between autoimmunity and preeclampsia?

Recent studies implicate an imbalance between regulatory and IL-17-producing CD4+T cells in the pathophysiology of preeclampsia. Regulatory T cells are decreased and autoimmune associated TH17 cells and IL-17 are increased in preeclamptic women vs. normal pregnant women. However, the stimulus for the imbalance among T helper cell subsets during preeclampsia is unknown and a role for IL-17 to increase blood pressure during pregnancy was previously undefined. This study was designed to test the hypothesis that placental ischemia is a stimulus for IL-17 producing Th17 cells and that IL-17 contributes to hypertension during pregnancy. Blood pressure (MAP) and CD4+T cells were assessed on day 19 of gestation from normal pregnant (NP) and placental ischemic RUPP rats. FACS was used to analyze CD4+ T cells and IL-17 was determined via ELISA from RUPP and NP plasma. MAP increased from 106+2 NP to 125+2mmHg RUPP (P<0.01). CD4+TH17 T cells increased to 22+8 RUPP vs 7+2 mmHg in NP rats (P<.05). IL-17 increased to 708+79 RUPP vs 547+64pg/ml in NP rats. IL-17 (100pg/kg/day) was infused via miniosmotic pump from day 14 to day 19 of gestation into NP rats. Excess IL-17 significantly increased MAP from 105+3 NP to 119+4 mmHg IL-17 infused (P<0.02). These data support the hypothesis that IL-17 and TH17 cells stimulated in response to placental ischemia may play an important role in mediating hypertension during pregnancy.

Glycogen Synthase Kinase-3 Is an Early Determinant in the Differentiation of Pathogenic Th17 Cells

CD4(+) T cells are critical for host defense but are also major drivers of immune-mediated diseases. The classical view of Th1 and Th2 subtypes of CD4(+) T cells was recently revised by the identification of the Th17 lineage of CD4(+) T cells that produce IL-17, which have been found to be critical in the pathogenesis of autoimmune and other diseases. Mechanisms controlling the differentiation of Th17 cells have been well described, but few feasible targets for therapeutically reducing Th17 cells are known. The generation of Th17 cells requires IL-6 and activation of STAT3. During polarization of CD4(+) T cells to Th17 cells, we found that inhibition of glycogen synthase kinase-3 (GSK3) blocked IL-6 production, STAT3 activation, and polarization to Th17 cells. Polarization of CD4(+) T cells to Th17 cells increased by 10-fold the expression of GSK3β protein levels in Th17 cells, whereas GSK3β was unaltered in regulatory T cells. Diminishing GSK3 activity either pharmacologically or molecularly blocked Th17 cell production, and increasing GSK3 activity promoted polarization to Th17 cells. In vivo inhibition of GSK3 in mice depleted constitutive Th17 cells in intestinal mucosa, blocked Th17 cell generation in the lung after Francisella tularensis infection, and inhibited the increase in spinal cord Th17 cells and disease symptoms in the experimental autoimmune encephalomyelitis mouse model of multiple sclerosis. These findings identify GSK3 as a critical mediator of Th17 cell production and indicate that GSK3 inhibitors provide a potential therapeutic intervention to control Th17-mediated diseases.

CRAC Channel Function Through ORAI1, STIM1 and STIM2 is Required for Proinflammatory Effector T Cell Function in Autoimmunity

ORAI1 constitutes the pore forming subunit of the Ca2+ release activated Ca2+ (CRAC) channel, which is responsible for store-operated Ca2+ entry (SOCE) in many cell types. ORAI1 is activated by stromal interaction molecules (STIM) 1 and 2 following immunoreceptor triggering and depletion of ER Ca2+ stores. ORAI1, STIM1 and also STIM2 are essential mediators of SOCE and CRAC channel function in human and murine T lymphocytes. A role for ORAI1 and STIM1 in T cells in vivo has been inferred from in vitro studies of cells from human immunodeficient patients with mutations in ORAI1 and STIM1 and mice with targeted deletion of Orai1, Stim1 and Stim2 genes. Investigating the role of SOCE in T cells in the context of autoimmunity and inflammation, we find that mice with T-cell specific deletion of Stim1 or Stim2 are protected from experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. T cells lacking STIM1 or STIM2 failed to produce the proinflammatory cytokines IL-17 and IFNγ, which are crucial for the induction of EAE. SOCE is also required for the proliferation and homeostasis of IL-17 producing Th17 cells. ORAI1 is similarly critical for several aspects of T cell mediated immunity in vivo. Immune responses that depend on Th1, Th2 and Th17 cells were severely attenuated in Orai1-deficient mice expressing a non-functional form of the CRAC channel. Orai1-deficient mice tolerated skin allotransplants significantly longer than wildtype littermates. Furthermore, T cells from Orai1-deficient mice failed to induce colitis in a T-cell dependent adoptive transfer model of inflammatory bowel disease as they lacked production of IL-17, IFNγ and TNFα. Taken together, our findings demonstrate that ORAI1, STIM1 and STIM2 are critical mediators of proinflammatory T cell function and autoimmunity.

連続交通事故後に生じた汎発性脱毛 : Th1細胞とTh17細胞の増加とTh2細胞の減少との潜在的関連性

A 37-year-old Japanese man presented with alopecia after being involved in a traffic accident. An immunohistochemical study of the biopsy specimen demonstrated that CD8+ T cells infiltrated into hair follicles with satellite cell necrosis of keratinocytes. Four weeks after his initial visit, he again had another traffic accident. Despite the treatment with oral prednisolone and a topical steroid, the alopecia became universalis. Treatment with systemic and topical steroids was continued, and 12 weeks later, white vellus hairs grew over the whole scalp. Intracytoplasmic study revealed that there was a positive correlation between the severity of the alopecia and the increase of interferon-gamma producing Th1 cells or interleukin (IL)-17 producing Th17 cells, whereas the number of IL-4 expressing Th2 cells was inversely proportional to the extent of alopecia. The autoimmune hair loss might occur via the activation of T helper 1 (Th1) and Th17 cells.

Lineage-specific Effects of 1,25-Dihydroxyvitamin D3 on the Development of Effector CD4 T Cells

Vitamin D deficiency is implicated in autoimmune disease. We therefore evaluated the effects of 1α,25-dihydroxyvitamin D(3) (1,25-D(3)), the active form of vitamin D, on the development of T helper 1 (Th1), Th17, and Th9 cells, which are implicated in the pathogenesis of different types of autoimmunity. 1,25-D(3) compromised the development of Th17 and Th9 cells, including IL-22-expressing cells while simultaneously increasing the frequency of IL-10-competent cells. Relative to Th17 and Th9 cells, the effects of 1,25-D(3) on Th1 cells were modest, reflecting the significantly reduced levels of the receptor for vitamin D in this lineage. The use of cells deficient in IL-10 or antibodies that block IL-10 signaling abolished the inhibitory effect of 1,25-D(3) on Th9 cells but had no effect on inhibition of Th17 cell frequencies. Thus, the induction of IL-10 in cultures of Th9 cells is an important mechanism by which 1,25-D(3) compromises Th9 development but does not explain inhibition of Th17 cells. A survey of select representatives of the Th17 transcriptome revealed that the levels of mRNA that encode RORγt, IL-17A, IL-17F, IL-23R, and IL-22, were reduced by 1,25-D(3), whereas IL-21 and aryl hydrocarbon receptor mRNA remained unchanged. These data suggest that vitamin D deficiency may promote autoimmunity by favoring the inordinate production of Th17 and Th9 cells at the expense of regulatory IL-10-producing T cells.

Functional and Pathogenic Differences of Th1 and Th17 Cells in Experimental Autoimmune Encephalomyelitis

BackgroundThere is consensus that experimental autoimmune encephalomyelitis (EAE) can be mediated by myelin specific T cells of Th1 as well as of Th17 phenotype, but the contribution of either subset to the pathogenic process has remained controversial. In this report, we compare functional differences and pathogenic potential of “monoclonal” T cell lines that recognize myelin oligodendrocyte glycoprotein (MOG) with the same transgenic TCR but are distinguished by an IFN-γ producing Th1-like and IL-17 producing Th17-like cytokine signature.Methods and FindingsCD4+ T cell lines were derived from the transgenic mouse strain 2D2, which expresses a TCR recognizing MOG peptide 35–55 in the context of I-Ab. Adoptive transfer of Th1 cells into lymphopenic (Rag2−/−) recipients, predominantly induced “classic” paralytic EAE, whereas Th17 cells mediated “atypical” ataxic EAE in approximately 50% of the recipient animals. Combination of Th1 and Th17 cells potentiated the encephalitogenicity inducing classical EAE exclusively. Th1 and Th17 mediated EAE lesions differed in their composition but not in their localization within the CNS. While Th1 lesions contained IFN-γ, but no IL-17 producing T cells, the T cells in Th17 lesions showed plasticity, substantially converting to IFN-γ producing Th1-like cells. Th1 and Th17 cells differed drastically by their lytic potential. Th1 but not Th17 cells lysed autoantigen presenting astrocytes and fibroblasts in vitro in a contact-dependent manner. In contrast, Th17 cells acquired cytotoxic potential only after antigenic stimulation and conversion to IFN-γ producing Th1 phenotype.ConclusionsOur data demonstrate that both Th1 and Th17 lineages possess the ability to induce CNS autoimmunity but can function with complementary as well as differential pathogenic mechanisms. We propose that Th17-like cells producing IL-17 are required for the generation of atypical EAE whereas IFN-γ producing Th1 cells induce classical EAE.

Azacitidine Induces A Shift In Th1/Th17 Ratio and FoxP3 Expression In Anti-CD3 Stimulated CD4+ T-Cells; Implications for the Treatment of Myelodysplastic Syndromes

AbstractAbstract 4026Aberrant DNA methylation and other epigenetic changes play a role in the development of myelodysplastic syndromes (MDS). Epigenetic drugs such as DNA methyltransferase inhibitors are therefore increasingly employed in MDS treatment regimens. Recent studies show that gene methylation processes also regulate T-cell function. Here we analyzed the in vitro effects of the DNA methyltransferase inhibitor '5-azacitidine (Aza) on CD4+ T-cell activation. We confirmed the previously described inhibition of proliferation and increased expression of FoxP3, the regulatory T-cell (Treg) marker, by anti-CD3 stimulated T-cells in the presence of 1mM Aza. Here we have sorted CD4+ T-cells isolated form healthy donor peripheral blood into CD25neg resting, CD25dim recently activated and CD25hi Treg cells. Aza facilitated the induction of CD25hiFoxP3+ T-cells from CD25neg (4.7% of vehicle treated cells versus 17.3% of Aza treated cells p=0.0007, n=9) and to a lesser extend from CD25dim (1.2% versus 8.6%, p=0.0015, n=7) CD4+ T-cells, while Aza had no effect on FoxP3 expression in CD25hi sorted cells, FoxP3 expression remained high. In addition, cytokine producing T-cells were enumerated after stimulation with phorbol-12-myristate-13-acetate (PMA) and ionomycin in the presence of Brefeldin A. Aza treatment increased the number of IFNγ producing cells in the total CD4+ population (19.1% versus 40.8%; p<0.0001, n=10) as well as among the CD25neg (5.7% vs 41.2%; p=0.001, n=8) and CD25dim CD4+ T-cell populations (28.4% versus 46.6%; p=0.06, n=7). TNFα producing cells were increased in the total CD4+ (36.4% versus 51.1%; p=0.011, n=9) and CD4posCD25dim (36.7% versus 52.3%; p=0.033, n=6) populations but not in the CD4posCD25neg cells (50.9% versus 51.1%; p=0.9, n=7). This increase in pro-inflammatory cytokine production indicates that Aza induces T-cell activation and that the increase in FoxP3 expression may reflect T-cell activation rather than an increase in bona fide Treg by Aza treatment. Indeed a proportion of the FoxP3+ cells was positive for TNFa or IFNg, suggesting that these are activated T-cells rather than Treg. However, the proportion of FoxP3+IFNγ- and FoxP3+TNFα- cells was significantly higher among Aza treated CD4+ cells (p=0.0037 and 0.0018 respectively, n=5), suggesting an increase in Treg as well. Functional assays to demonstrate that these FoxP3+ cells are indeed regulatory T-cells are currently being set up. Next to IFNγ and TNFα producing Th1 cells, the more recently described IL-17 committed Th17 cells have been described to play a role in low risk MDS. Furthermore, it has been shown that Treg can differentiate into IL-17 producing cells. We, therefore evaluated the effect of Aza on Th17 cells. Interestingly, in contrast to IFNγ and TNFα producing cells, the proportion of IL-17+IFNγ- Th17 cells among the total CD4+ population was reduced by Aza treatment (1.8% versus 1.1% p=0.035, n=10), leading to a significant increase in the Th1/Th17 ratio (14.0 versus 47.9, p=0.0005, n=10). In contrast, although the numbers were small, the proportion of Th17 cells was increased by Aza in the CD25neg population (0.08% versus 0.20%, p=0.028, n=8), suggesting that Aza may have differential effects on resting and recently activated T-cells. In conclusion, our data show that Aza increases the induction of FoxP3+ Treg and Th1 cells but inhibits IL-17 production, particularly by previously activated T-cells. Aza may therefore particularly be beneficial in pathogenic immune disorders characterized by increased Th17 numbers accompanied by reduced Treg frequencies, such as low-risk MDS. Disclosures:No relevant conflicts of interest to declare.

Interleukin-17 and TH17 Pathway Supports Waldenstrom's Macroglobulinemia Cell-Growth: Potential Therapeutic Implications

AbstractAbstract 446Waldenstrom's macroglobulinemia (WM), similar to multiple myeloma (MM), is associated with immune dysfunction. Both T and B cell dysfunctions are reported with suppressed uninvolved immunoglobulin, and inadequate vaccine and T cell responses. Although some mechanisms mediating immune dysregulation in WM have been studied, its molecular and cellular basis remains ill defined. Similarly, number of inflammatory cytokines and chemokines has been implicated in this process, but their effect on WM cell growth and immune function has not been well characterized. Recently, TH17 cells, a new CD4 cell population, has been identified by the presence of IL-17. TH17 cells play an important role in auto-immunity and in the development of anti-tumor immunity. As TH17 cells support MM cell growth and induce immune dysfunction in MM, we have evaluated the the role of TH17 cells and associated pro-inflammatory cytokines in WM. We first analyzed T helper cell subsets (TH1, TH2, and TH17) in freshly isolated PBMC from WM, and observed that all three cell types were decreased in WM compared with normal donors. Particularly, the IFN-γ producing TH1 cells from patients with WM were significantly reduced compared to normal donors (11±2% vs 30±3% respectively, P<0.01). However, unlike MM, IL-17 producing TH17 cell numbers were reduced in PBMC from WM patients (n=8) compared to PBMC from normal donors (n=8) and patients with MM (n=11), (1.5±0.5 vs 2.5±0.5% vs 4.50±0.8% respectively; p<0.05). Furthermore, when we polarized isolated naïve CD4 cells from WM patients using TH17 polarizing cocktail consisting of IL-6, IL-1β, IL-23 and TGF-β to induce TH17 cells differentiation, WM patients, unlike MM patients, showed significantly lower induction of TH17 cells in CD4 population compared to normal donor TH17 cells (0.3±0.1% WM; 11.9±2 % MM and 3.6±0.7% ND). Next, we evaluated the serum levels of cytokines and chemokines in sera from patients with WM in comparison with normal donors. The sera from WM patients showed significantly elevated levels of IL-2 (5 folds), IL-15 (2 folds) and GM-CSF (2 folds) among 19 cytokines, compared with sera from normal donors. When we evaluated TH17 cell-associated cytokines, both IL-1-beta (3 folds) and IL-17 (2 folds) were significantly elevated in sera from WM patients compared with sera from normal donors. In addition, we observed modulation of chemokines including, MCP-1, MIP-1, Eotaxin and RANTES in sera from WM patients. Finally, when we cultured WM cell-line in the presence or absence of IL-17 with or without stromal cells, we observed significant induction of WM cell proliferation by IL-17 and its inhibition by anti-IL17 antibody. These data shows that although similar to MM, there is immune dysfunction in WM, the mechanisms driving these effects especially cytokine milieu, and TH17 cell population are different between MM and WM. Disclosures:Treon:Millennium Pharmaceuticals, Genentech BiOncology, Biogen IDEC, Celgene, Novartis, Cephalon: Consultancy, Honoraria, Research Funding; Celgene Corporation: Research Funding; Novartis Corporation: Research Funding; Genentech: Consultancy, Research Funding. Munshi:Millennium Pharmaceuticals: Honoraria, Speakers Bureau.

A Critical Function of Th17 Proinflammatory Cells in the Development of Atherosclerotic Plaque in Mice

Considerable evidence supports that the CD4(+) T cell-mediated immune response contributes to the development of atherosclerotic plaque. However, the effects of Th17 cells on atherosclerosis are not thoroughly understood. In this study, we evaluated the production and function of Th17 and Th1 cells in atherosclerotic-susceptible ApoE(-/-) mice. We observed that the proportion of Th17 cells, as well as Th1, increased in atherosclerotic ApoE(-/-) mice compared with nonatherosclerotic wild-type littermates. In ApoE(-/-) mice with atherosclerosis, the expression of IL-17 and retinoic acid-related orphan receptor γt was substantially higher in the arterial wall with plaque than in the arterial wall without plaque. Increased Th17 cells were associated with the magnitude of atherosclerotic plaque in ApoE(-/-) mice. Importantly, treatment of ApoE(-/-) mice with neutralizing anti-IL-17 Ab dramatically inhibited the development of atherosclerotic plaque, whereas rIL-17 application significantly promoted the formation of atherosclerotic plaque. These data demonstrate that Th17 cells play a critical role in atherosclerotic plaque formation in mice, which may have implications in patients with atherosclerosis.

Leishmania Exosomes Modulate Innate and Adaptive Immune Responses through Effects on Monocytes and Dendritic Cells

We investigated the properties of leishmania exosomes with respect to influencing innate and adaptive immune responses. Exosomes from Leishmania donovani modulated human monocyte cytokine responses to IFN-γ in a bimodal fashion by promoting IL-10 production and inhibiting that of TNF-α. Moreover, these vesicles were inhibitory with respect to cytokine responses (IL-12p70, TNF-α, and IL-10) by human monocyte-derived dendritic cells. Exosomes from wild-type (WT) L. donovani failed to prime monocyte-derived dendritic cells to drive the differentiation of naive CD4 T cells into IFN-γ-producing Th1 cells. In contrast, vesicles from heat shock protein (HSP)100(-/-) L. donovani showed a gain-of-function and proinflammatory phenotype and promoted the differentiation of naive CD4 lymphocytes into Th1 cells. Proteomic analysis showed that exosomes from WT and HSP100(-/-) leishmania had distinct protein cargo, suggesting that packaging of proteins into exosomes is dependent in part on HSP100. Treatment of C57BL/6 mice with WT L. donovani exosomes prior to challenge with WT organisms exacerbated infection and promoted IL-10 production in the spleen. In contrast, HSP100(-/-) exosomes promoted spleen cell production of IFN-γ and did not adversely affect hepatic parasite burdens. Furthermore, the proparasitic properties of WT exosomes were not species specific because BALB/c mice exposed to Leishmania major exosomes showed increased Th2 polarization and exacerbation of disease in response to infection with L. major. These findings demonstrate that leishmania exosomes are predominantly immunosuppressive. Moreover, to our knowledge, this is the first evidence to suggest that changes in the protein cargo of exosomes may influence the impact of these vesicles on myeloid cell function.

Patients with non-relapsing ANCA-associated vasculitis have increased numbers of circulating IL-10 producing Th17 cells

IL-17 producing T-cells (Th17) were recently defined as a new, pro-inflammatory T-cell subset and are considered to have a key role in autoimmune diseases. Importantly, it was recently described that anti-inflammatory regulatory T-cells (Treg) are able to convert to pro-inflammatory Th17 cells (“Plasticity”) and vice versa. Little is known about the Th17 response or plasticity in ANCA-associated vasculitis (AAV). Therefore, we investigated Th17 responses in AAV.

IL-23 modulated myelin-specific T cells induce EAE via an IFNγ driven, IL-17 independent pathway

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory demyelinating disease of the central nervous system (CNS) mediated by myelin-reactive CD4 + T cells. An unresolved issue that has important clinical implications concerns the cytokines produced by myelin-reactive T cells that determine their pathogenicity. Initially, IL-12 polarized, IFNγ producing Th1 cells were thought to be essential for the development of EAE. More recently, IL-23 polarized, IL-17 producing Th17 cells have been highlighted as critical encephalitogenic effectors. There is growing evidence that parallel autoimmune pathways can result in common clinical and histopathological endpoints. In the current study, we describe a form of EAE induced by the transfer of IL-23 modulated CD4 + T cells into IL-17 receptor (IL-17R) deficient hosts. We found that IL-23 stimulates myelin-reactive T cells to produce both IFNγ and IL-17. Surprisingly, in this model the development of EAE is IFNγ dependent. Our findings illustrate a novel mechanism by which IL-23 promotes encephalitogenicity and they further expand the spectrum of autoreactive T cells capable of mediating inflammatory demyelinating disease of the CNS.

A novel subset of CD4+ TH2 memory/effector cells that produce inflammatory IL-17 cytokine and promote the exacerbation of chronic allergic asthma

The inflammatory cytokine interleukin (IL)-17 is involved in the pathogenesis of allergic diseases. However, the identity and functions of IL-17-producing T cells during the pathogenesis of allergic diseases remain unclear. Here, we report a novel subset of T(H)2 memory/effector cells that coexpress the transcription factors GATA3 and RORγt and coproduce T(H)17 and T(H)2 cytokines. Classical T(H)2 memory/effector cells had the potential to produce IL-17 after stimulation with proinflammatory cytokines IL-1β, IL-6, and IL-21. The number of IL-17-T(H)2 cells was significantly increased in blood of patients with atopic asthma. In a mouse model of allergic lung diseases, IL-17-producing CD4(+) T(H)2 cells were induced in the inflamed lung and persisted as the dominant IL-17-producing T cell population during the chronic stage of asthma. Treating cultured bronchial epithelial cells with IL-17 plus T(H)2 cytokines induced strong up-regulation of chemokine eotaxin-3, Il8, Mip1b, and Groa gene expression. Compared with classical T(H)17 and T(H)2 cells, antigen-specific IL-17-producing T(H)2 cells induced a profound influx of heterogeneous inflammatory leukocytes and exacerbated asthma. Our findings highlight the plasticity of T(H)2 memory cells and suggest that IL-17-producing T(H)2 cells may represent the key pathogenic T(H)2 cells promoting the exacerbation of allergic asthma.

The deregulation of regulatory T cells on interleukin-17-producing T helper cells in patients with unexplained early recurrent miscarriage

CD4(+)CD25(+) regulatory T cells (Tregs) are important for the maintenance of immune homeostasis by virtue of their ability to control T-cell proliferation in the peripheral blood (PB). We recently demonstrated that the prevalence of Tregs is decreased, whereas that of Th17 cells is increased, in the PB and decidua samples of patients with unexplained recurrent miscarriage (RM). In this study, we investigated whether the cytokine production of Th17 cells can be suppressed by the Tregs and elucidated the mechanism by which Tregs exert this suppressive effect. Flow cytometry was used to analyze the surface phenotype and cytokine production of Th17 cells in the PB of women with unexplained RM (n = 17) and healthy women in early stages of pregnancy who underwent elective abortion (n = 20). The suppressive ability of Tregs on Th17 cells was assessed in in vitro co-cultures and transwell experiments. The amount of secreted interleukin-17 (IL-17) in the supernatants was measured by enzyme-linked immunosorbent assay (ELISA). The inhibitory activity of transforming growth factor-β (TGF-β) and IL-10 on IL-17 expression in CD4(+) T cells was assessed using ELISA. The proportions of IL-17-positive CD4(+) T cells, CC chemokine receptor type 6 (CCR6)-positive CD4(+) T cells and CCR6 expression of IL-17-positive CD4(+) T cells were higher in the PB samples of patients with unexplained RM than in PB of healthy control subjects. In vitro, Tregs could inhibit the expression of IL-17; more Th17 cells were inhibited in the control group than in the unexplained RM group. High-dose TGF-β inhibited the expression of IL-17, whereas IL-10 inhibited IL-17 expression in a dose-dependent manner. IL-17 expression can be inhibited by Tregs. The suppressive activity of Tregs on Th17 cells was decreased in patients with unexplained RM. The ability of Tregs to suppress cytokine secretion might be effected by a cell-cell contact. TGF-β and IL-10 could inhibit the expression of IL-17.

Tim-3/Galectin-9 Pathway: Regulation of Th1 Immunity through Promotion of CD11b+Ly-6G+ Myeloid Cells

IFN-gamma plays a central role in antitumor immunity. T cell Ig and mucin domain (Tim-3) is expressed on IFN-gamma-producing Th1 cells; on interaction with its ligand, galectin-9, Th1 immunity is terminated. In this study, we show that transgenic overexpression of Tim-3 on T cells results in an increase in CD11b(+)Ly-6G(+) cells and inhibition of immune responses. Molecular characterization of CD11b(+)Ly-6G(+) cells reveals a phenotype consistent with granulocytic myeloid-derived suppressor cells. Accordingly, we find that modulation of the Tim-3/galectin-9 (Gal-9) pathway impacts on tumor growth. Similarly, overexpression of Tim-3 ligand, Gal-9, results in an increase in CD11b(+)Ly-6G(+) cells and inhibition of immune responses. Loss of Tim-3 restores normal levels of CD11b(+)Ly-6G(+) cells and normal immune responses in Gal-9 transgenic mice. Our data uncover a novel mechanism by which the Tim-3/Gal-9 pathway regulates immune responses and identifies this pathway as a therapeutic target in diseases where myeloid-derived suppressor cells are disadvantageous.