Altered microRNA Expression and Immunosuppressive Cytokine Production by Regulatory T Cells of Ulcerative Colitis Patients

Regulatory T (Treg) cells are essential for maintenance of peripheral tolerance and prevention of autoimmune diseases in part by producing immunosuppressive cytokines. Recently, microRNAs (miRNAs) have also been involved in autoimmune disorders, not least for their crucial role in the regulation of Treg biology and function. We simultaneously investigated the concentration of IL-35, IL-10, TGF-β, and sCD25 in supernatant of cell culture and the expression patterns of several miRNAs in CD4⁺CD25⁺ CD127^?/low FoxP3⁺ Tregs of ulcerative colitis (UC) patients. Significantly lower levels of IL-10 and IL-35 were observed in Treg cultures of UC patients. miR-21, miR-146a, and miR-155 levels were downregulated and miR-31 level was upregulated in Tregs of patients. Our results suggest that microRNAs may serve as a novel regulator in function and homoeostasis of UC Treg cells, providing a key role for them in pathophysiology of UC.     

Protective and Pathological Functions of CD8+ T Cells in Leishmania braziliensis Infection

Cutaneous leishmaniasis (CL) caused by Leishmania braziliensis is characterized by a strong Th1 response that leads to skin lesion development. In areas where L. braziliensis transmission is endemic, up to 15% of healthy subjects have tested positive for delayed-type hypersensitivity to soluble leishmania antigen (SLA) and are considered to have subclinical (SC) infection. SC subjects produce less gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) than do CL patients, but they are able to control the infection. The aim of this study was to characterized the role of CD8⁺ T cells in SC infection and in CL. Peripheral blood mononuclear cells (PBMC) were stimulated with SLA to determine the frequencies of CD4⁺ IFN-γ⁺ and CD8⁺ IFN-γ⁺ T cells. Monocytes from PBMC were infected with L. braziliensis and cocultured with CD8⁺ T cells, and the frequencies of infected monocytes and levels of cytotoxicity markers, target cell apoptosis, and granzyme B were determined. The frequency of CD8⁺ IFN-γ⁺ cells after SLA stimulation was higher for SC individuals than for CL patients. The frequency of infected monocytes in SC cells was lower than that in CL cells. CL CD8⁺ T cells induced more apoptosis of infected monocytes than did SC CD8⁺ T cells. Granzyme B production in CD8⁺ T cells was higher in CL than in SC cells. While the use of a granzyme B inhibitor decreased the number of apoptotic cells in the CL group, the use of z-VAD-FMK had no effect on the frequency of these cells. These results suggest that CL CD8⁺ T cells are more cytotoxic and may be involved in pathology.     

Upregulated IL-17A secretion and CCR6 co-expression in Treg subsets are related to the imbalance of Treg/Th17 cells in active UC patients

Ulcerative colitis (UC) is an idiopathic, chronic inflammatory disease, which is characterized with overactive immune response. It is well established that the imbalance between Tregs and Th17 cells plays a pivotal role in pathogenesis of UC. In this study, we investigated the impact of functional changes in Treg subsets on Treg/Th17 ratio and further explored their clinical significance in the activity of UC. Treg subsets were comprehensively analysed using flow cytometry and in vitro cultured in both active and remission UC patients, of which nine active UC patients were further followed up. The correlation analyses were performed to explore the potential associations between Treg subsets and clinical indicators, as well as the impact of serum cytokines, detected by ELISA, on IL-17A secretion and CCR6 co-expression of Treg subsets. In active UC patients, we found CD45RA^-FoxP3^hiTregs were obviously decreased and inversely correlated with disease activity, while CD45RA⁺FoxP3^loTregs were increased and positively correlated with disease activity. Meanwhile, IL-17A secretion and CCR6 co-expression levels in Tregs were significantly increased in active UC. Moreover, Tregs co-expressing CCR6 possesses higher level of IL-17A secretion. In nine followed up patients, we observed downregulated IL-17A secreting and CCR6 co-expression when achieving remission from active stage. In addition, IL-17A⁺FoxP3⁺ and IL-17A⁺FoxP3⁺CCR6⁺Tregs were positively correlated with serum IL-21 and disease activity, respectively. These findings suggested that upregulated IL-17A secretion and CCR6 co-expression in Treg subsets may be related to the imbalance between Tregs and Th17 cells and associated with the disease activity in UC patients.     

Interleukin-10-dependent down-regulation of interferon-gamma response to Leishmania by Mycobacterium leprae antigens during the clinical course of a coinfection

We have described a case of a patient with an intriguing association of mucocutaneous leishmaniasis with lepromatous leprosy, two opposite polar forms of these spectral diseases. In the present follow-up study, we investigated the effect of the addition of Mycobacterium leprae antigens on interferon-gamma (IFN-γ) production in Leishmania antigen-stimulated cultures of peripheral blood mononuclear cells (PBMC) from this patient. For this purpose, PBMC cultures were stimulated with crude L. braziliensis and/or M. leprae whole-cell antigen extracts or with concanavalin A. In some experiments, neutralizing anti-human interleukin (IL)-10 antibodies were added to the cultures. IFN-γ and IL-10 levels in culture supernatants were measured by ELISA. During active leprosy, M. leprae antigens induced 72.3% suppression of the IFN-γ response to L. braziliensis antigen, and this suppression was abolished by IL-10 neutralization. Interestingly, the suppressive effect of M. leprae antigen was lost after the cure of leprosy and the disappearance of this effect was accompanied by exacerbation of mucosal leishmaniasis. Considered together, these results provide evidence that the concomitant lepromatous leprosy induced an IL-10-mediated regulatory response that controlled the immunopathology of mucosal leishmaniasis, demonstrating that, in the context of this coinfection, the specific immune response to one pathogen can influence the immune response to the other pathogen and the clinical course of the disease caused by it. Our findings may contribute to a better understanding of the Leishmania/M. leprae coinfection and of the immunopathogenesis of mucosal leishmaniasis.     

Distinct different sensitivity of Treg and Th17 cells to Fas-mediated apoptosis signaling in patients with acute coronary syndrome

Objective: An imbalance in CD4⁺CD25⁺ regulatory T (Treg) cells and Th17 cells has been found to correlate to occurrence of acute coronary syndrome [ACS, including unstable angina (UA) and acute myocardial infarction (AMI)]. However, the mechanisms of Th17/Treg imbalance in ACS patients are still unclear. The purpose of this study is to investigate the possibility of differences in sensitivity of Th17 and Tregs to Fas-mediated apoptosis which could lead to Th17/Treg imbalance in ACS patients. Methods: We examined the apoptosis of Th17 and Treg cells, apoptosis-related Fas/Fas ligand(FasL) pathway, and inflammatory markers in patients with AMI, UA, stable angina (SA) and controls by Flow cytometry and ELISA. Then we analysed the correlation of inflammatory markers and sFasL to Treg apoptosis, and the effect of anti-FasL antibody on Treg apoptois in vitro. Results: Our study demonstrated that apoptotic Tregs, Fas and FasL expression, Caspase-3 activity of Tregs were significantly higher in ACS patients than those in NCA and SA patients (all P < 0.05). The percentage of apoptotic Tregs is positively correlated with the levels of inflammatory markers and sFasL. In vitro incubation of peripheral blood mononuclear cells from ACS patients with anti-FasL antibody resulted in a markedly reduction of apoptotic Treg cells. However, there were no significant differences in apoptotic Th17 cells and in Fas and FasL expression for Th17 cells between the four groups (all P >0.05). Conclusions: Tregs, but not Th17 cells, become apoptotic through Fas/FasL pathway, which contributed to reduction of Tregs leading to an imbalance between Th17 and Treg cells. This could be the mechanism underlying Th17/Treg imbalance and occurrence of ACS.     

Dichotomy of the human T cell response to leishmania antigens. II. Absent or Th2-like response to gp63 and Th1-like response to lipophosphoglycan-associated protein in cells from cured visceral leishmaniasis patients

The T cell response to different Leishmania donovani antigens was investigated using peripheral blood mononuclear cells (PBMC) from Kenyans cured of visceral leishmaniasis and non-exposed Danes. Crude promastigote and amastigote antigens both induced proliferation and interferon-gamma (IFN-γ) production in PBMC from cured patients, while cells from non-exposed donors gave weak responses. A similar pattern was induced by lipophosphoglycan-associated protein (LPGAP). By contrast, the major surface protease of Leishmania, gp63, induced only a weak proliferative response without IFN-γ production in five of 17 samples from cured patients. Four of the five responding cultures produced IL-4, i.e. the response to this antigen was of the Th2 type. Furthermore, sera from acutely ill visceral leishmaniasis patients contained high levels of IgG antibodies to gp63. The Th2-like response to gp63 in patients cured of visceral leishmaniasis differs from the Th1-like response to the same antigen observed in patients cured of cutaneous leishmaniasis.     

美沙拉嗪对DSS诱导小鼠溃疡性结肠炎模型Th1、Th17及Treg细胞亚群的影响

 目的:观察葡聚糖硫酸钠（DSS）诱导小鼠溃疡性结肠炎（UC）模型中辅助性T细胞（Th1、Th17亚群）及调节性T细胞（Treg）细胞亚群的变化,探讨美沙拉嗪（MSLZ）治疗UC的免疫学机制。方法: 采用流式细胞分析术检测DSS诱导的小鼠UC模型结肠组织及外周血单个核细胞中白细胞介素17（IL-17）、γ-干扰素（IFN-γ）及核转录因子Foxp3的表达,并检测MSLZ预治疗对小鼠UC 模型Th1、Th17和Treg亚群的影响。结果: 在DSS诱导的小鼠UC模型中,其外周血单个核细胞（PBMC）中CD3+T细胞高表达IL-17、IFN-γ及Foxp3,肠黏膜单个核细胞（LPMC）中CD3+T细胞高表达IFN-γ和Foxp3,但IL-17的表达与对照组无差异。进一步发现UC模型小鼠LPMC中Th17、Th1和Treg均显著高于对照组,但PBMC中只有Treg高于对照组。MSLZ预治疗能显著下调UC 模型小鼠PBMC和LPMC中Th17、Th1和Treg细胞亚群。结论: DSS诱导的小鼠 UC模型中CD4+T细胞亚群Th1、Th17及Treg细胞显著升高,提示CD4+T细胞亚群在UC发病中起重要作用,美沙拉嗪可能通过调节Th1、Th17及Treg细胞亚群发挥抗炎及治疗UC作用。     

Clinical,molecular, and T cell subset analyses in a small cohort of Chinese patients with hyper-IgM syndrome type 1

Type 1 hyper-IgM syndrome (HIGM1) is a rare primary immunodeficiency disease caused by mutations in the CD40L gene. Patients often present with recurrent infections and autoimmune manifestations. We investigated the clinical and molecular characteristics of HIGM1 in thirteen patients from the Chinese mainland and examined the proportion of CD4⁺CD25⁺FoxP3⁺Treg, Th17, and Th1 cells in the peripheral blood. We identified ten distinct CD40L mutations in eleven patients: one missense mutation, one nonsense mutation, one insertion mutation (in frame), and seven deletions. Six of these mutations were novel. We observed the percentage of Tregs in the peripheral blood of HIGM1 patients decreased markedly compared with that in healthy controls, but no statistically significant differences was found in the percentages of Th17 and Th1. The identified mutations reflect the heterogeneity of the CD40L gene in HIGM1. Precise genetic diagnosis of HIGM1 will enable appropriate therapeutic interventions, reliable detection of carriers, and genetic counseling. Skewed Treg, Th17/Treg, and Th1/Treg profiles may be associated with immune responses to autoimmunity or infection, which requires replication in larger studies.     

Regulatory T cells reduce endothelial neutral sphingomyelinase 2 to prevent T-cell migration into tumors

Endothelial cells are key regulators of transendothelial migration and their secretion of chemokines and expression of adhesion molecules facilitates lymphocyte entry into tissues. Previously, we demonstrated that Tregs can reduce transendothelial migration of T cells into tumors by decreasing endothelial CXCL10 secretion, but the mechanism by which this occurs is still not known. In this study, we aimed to define how Tregs decrease transendothelial migration into tumors. mRNA sequencing of intestinal tumor endothelial cells from Treg depleted mice identified neutral sphingomyelinase 2 (nSMase2) as a gene downregulated in the presence of Tregs. nSMase2 is expressed in human umbilical vein endothelial cells (HUVECs) and was decreased after coculture with Tregs. Furthermore, blocking of nSMase2 activity in vitro decreased VCAM1, CX3CL1, and CXCL10 expression in HUVECs, mirroring the same decrease found in Treg cocultures. In the APC^min/+ mouse model of intestinal cancer, nSMase2 is lower in tumor endothelial cells than in unaffected small intestine and chronic treatment with a nSMase2 inhibitor suppressed the increased migration that is otherwise seen in the absence of Tregs. We conclude that nSMase2 is an important mediator in endothelial cells supporting transendothelial migration, which may be targeted by Tregs to reduce T-cell migration into tumors.     

Presence of parasite DNA in clinically unaffected nasal mucosa during cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis

Objectives

We aimed to detect Leishmania DNA carriage in nasal mucosa of individuals with cutaneous leishmaniasis (CL) caused by Leishmania (Viannia) braziliensis.

Intestine-derived Clostridium leptum induces murine tolerogenic dendritic cells and regulatory T cells in vitro

Patients with autoimmune and allergic diseases frequently present with reduced numbers and functionally impaired regulatory T cells (Tregs) and/or tolerogenic dendritic cells (tDCs). tDC-mediated regulation of Treg proliferation (numbers) and activation is crucial to establishing and maintaining an appropriate level of immune tolerance. Colonic colonization of Clostridium spp. is associated with accumulation of Tregs, which inhibits development of inflammatory lesions. To investigate whether infection with the Clostridium leptum sp. can specifically induce Tregs and/or tDCs bone marrow-derived dendritic cells were cultured in the presence or absence of C. leptum then co-cultured with CD4⁺CD25⁻ T cells or not. Changes in tDC numbers, Treg numbers, percentages of T cell subsets, and expression of cytokines related to Tregs (IL-10 and transforming growth factor-beta (TGF-β1)), DCs (IL-12p40 and IL-6) and effector T cells (IFN-γ, IL-4, IL-5, IL-13, and IL-17A) were measured. In the co-culture system, C. leptum-stimulated tDCs were able to increase the percentage and total number of Tregs attenuate activation of T helper cells (Th1, Th2, and Th17), and decrease the amount of secreted IL-4, IL-5, IL-13, IFN-γ and IL-17A. Thus, C. leptum exposure can induce the tDC-mediated stimulation of Tregs while disrupting the immune inflammatory response mediated by Th1, Th2 and Th17 cells.     

Regulatory T cells and T helper 17 cells in viral infection

CD4⁺ T cells are the central element of the adaptive immune responses and protect the body from a variety of pathogens. Starting from naive cells, CD4⁺ T cells can differentiate into various effector cell subsets with specialized functions including T helper (Th) 1, Th2, Th17, regulatory T (Treg) and T follicular helper (Tfh) cells. Among them, Tregs and Th17 cells show a strong plasticity allowing the functional adaptation to various physiological and pathological environments during immune responses. Although they are derived from the same precursor cells and their differentiation pathways are interrelated, the terminally differentiated cells have totally opposite functions. Studies have shown that Tregs and Th17 cells have rather complex interplays in viral infection: Th17 cells may contribute to immune activation and disease progression while Tregs may inhibit this process and play a key role in the maintenance of immune homoeostasis, possibly at the cost of compromised viral control. In this review, we take respiratory syncytial virus (RSV), hepatitis B virus (HBV)/hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infections as examples to discuss these interplays and their impacts on disease progression in viral infection.     

T cell-specific BLIMP-1 deficiency exacerbates experimental autoimmune encephalomyelitis in nonobese diabetic mice by increasing Th1 and Th17 cells

Recently, we demonstrated that B lymphocyte-induced maturation protein 1 (BLIMP-1) has a role in regulating the differentiation and effector function of Th1 and Th17 cells. As these cells play critical roles in the induction and pathogenesis of experimental autoimmune encephalomyelitis (EAE), we investigated the potential role of T cell BLIMP-1 in modulating MOG_35–55-induced EAE. We established T cell-specific BLIMP-1 conditional knockout (CKO) NOD mice to dissect the role of BLIMP-1 in EAE using loss-of-function model. Our results indicate that EAE severity is dramatically exacerbated in CKO mice. The numbers of CNS-infiltrating Th1, Th17, IFN-γ⁺IL-17A⁺, and IL-21⁺IL-17A⁺ CD4⁺ T cells are remarkably increased in brain and spinal cord of CKO mice. Moreover, the ratio of Tregs/effectors and IL-10 production of Tregs are significantly downregulated in CNS of CKO mice. We conclude that BLIMP-1 suppresses autoimmune encephalomyelitis via downregulating Th1 and Th17 cells and impairing Treg cells.     

Deacetylase inhibition increases regulatory T cell function and decreases incidence and severity of collagen-induced arthritis

Collagen-induced arthritis (CIA) is an established mouse model of disease with hallmarks of clinical rheumatoid arthritis. Histone/protein deacetylase inhibitors (HDACi) are known to inhibit the pathogenesis of CIA and other models of autoimmune disease, although the mechanisms responsible are unclear. Regulatory T cell (Treg) function is defective in rheumatoid arthritis. FOXP3 proteins in Tregs are present in a dynamic protein complex containing histone acetyltransferase and HDAC enzymes, and FOXP3 itself is acetylated on lysine residues. We therefore investigated the effects of HDACi therapy on regulatory T cell function in the CIA model. Administration of an HDACi, valproic acid (VPA), significantly decreased disease incidence (p < 0.005) and severity (p < 0.03) in CIA. In addition, VPA treatment increased both the suppressive function of CD4⁺CD25⁺ Tregs (p < 0.04) and the numbers of CD25⁺FOXP3⁺ Tregs in vivo. Hence, clinically approved HDACi such as VPA may limit autoimmune disease in vivo through effects on the production and function of FOXP3⁺ Treg cells.     

Marine peptides as immunomodulators: Californiconus californicus-derived synthetic conotoxins induce IL-10 production by regulatory T cells (CD4+Foxp3+)

Abstract

Context: CD4⁺ T lymphocytes are able to differentiate into distinct subtypes according to several immunological scenarios, including T helper (Th)1, Th2, Th17 and regulatory T (Treg) cells. CD4⁺ T cells are phenotypically flexible and have specific ion channels, such as the nicotinic acetylcholine receptors (nAChR) that could be modulated by peptides produced by marine snails, known as conotoxins. Their effect on T lymphocytes has not been explored and emerging evidence suggests that these peptides may have immunomodulatory activities.

Objective: This study investigated the effect of two Californiconus californicus-derived synthetic conotoxins on the proliferation and differentiation of T lymphocyte subpopulations Th1, Th2, Th17 and Treg.

Methods: Cells from lymph nodes of BALB/c mice were cultured in the presence of conotoxins cal14.1b and cal14.2c (5.5?μM), during 96?h. Cell proliferation and intracellular cytokine production (IFN-γ, IL-4, IL-17 and IL-10) were analyzed by flow cytometry.

Results and Discussion: cal14.1b and cal14.2c increased intracellular IL-10 production in Treg (CD3⁺CD4⁺Foxp3⁺) cells and decreased intracellular IL-17 production (CD3⁺CD4⁺) after 72?h of culture. Conotoxins did not show any effect on T cell proliferation nor Th1/Th2 balance.

Conclusion: These results suggest that synthetic conotoxins exert immunomodulatory activity, especially by regulating specific functions on T lymphocytes.     

Downregulation of TGF-βRII in T effector cells leads to increased resistance to TGF-β-mediated suppression of autoimmune responses in type I diabetes

Tregs play an important role in controlling immune responses, particularly autoimmunity. In NOD mouse model, an excellent model for autoimmune diabetes, transfer of Tregs was shown to prevent diabetes, whereas depletion of Tregs in vivo enhanced disease progression, suggesting that Treg dysfunction contributes to the pathogenesis of diabetes. However, the mechanisms leading to Treg dysfunction and their role in diabetes progression has remained unclear. In this study we assessed quantitative and qualitative changes in Tregs during the development of autoimmune diabetes in NOD. We compared female NOD with males that have similar predisposition to but a lower incidence of diabetes and found that Treg numbers remained unchanged between 6 to 16 weeks of age in both groups. Although female Tregs produced lower TGF-β compared to male, regulatory function of female Tregs was only marginally inferior to male upon GAD65 autoantigen stimulation. GAD65-reactive female Teffectors were more responsive and progressively became refractory to regulation compared to male effectors, in part due to lower expression of TGF-β RII, accounting for reduced sensitivity to Tregs. Moreover, we unexpectedly found that TGF-β suppressed IFN-γ production to GAD65 antigen in male, not in female responders. These data suggest that TGF-β plays a major role in Teff resistance to regulation and Treg dysfunction, and may account for autoimmune diabetes. Our study implies that development of a successful supplemental Treg therapy for halting autoimmunity may require further understanding of Teff responses to regulation in order to generate highly effective Tregs.     

Immunopathogenesis of non-healing American cutaneous leishmaniasis and progressive visceral leishmaniasis

The outcomes of Leishmania infection are determined by host immune and nutrition status, parasite species, and co-infection with other pathogens. While subclinical infection and self-healing cutaneous leishmaniasis (CL) are common, uncontrolled parasite replication can lead to non-healing local lesions or visceral leishmaniasis (VL). It is known that infection control requires Th1-differentiation cytokines (IL-12, IL-18, and IL-27) and Th1 cell and macrophage activation. However, there is no generalized consensus for the mechanisms of host susceptibility. The recent studies on regulatory T cells and IL-17-producing cells help explain the effector T cell responses that occur independently of the known Th1/Th2 cell signaling pathways. This review focuses on the immunopathogenesis of non-healing American CL and progressive VL. We summarize recent evidence from human and animal studies that reveals the mechanisms of dysregulated, hyper-responses to Leishmania braziliensis, as well as the presence of disease-promoting or the absence of protective responses to Leishmania amazonensis and Leishmania donovani. We highlight immune-mediated parasite growth and immunopathogenesis, with an emphasis on the putative roles of IL-17 and its related cytokines as well as arginase. A better understanding of the quality and regulation of innate immunity and T cell responses triggered by Leishmania will aid in the rational control of pathology and the infection.     

Regulatory T cells in autoimmune neuroinflammation

Regulatory T cells are the central element for the maintenance of peripheral tolerance. Several subtypes of regulatory T (Treg) cells have been described, and most of them belong to the CD4⁺ T-helper (Th) cell lineage. These specific subtypes can be discriminated according to phenotype and function. Forkhead box protein 3 (FoxP3)-expressing natural Treg cells (Tregs) and IL-10-producing, T-regulatory type 1 cells (Tr1) are the best-studied types of CD4⁺ regulatory T cells in humans and experimental animal models. It was shown that they play a crucial role during autoimmune neuroinflammation. Both cells types seem to be particularly important for multiple sclerosis (MS). Here, we discuss the role of CD4⁺ regulatory T cells in autoimmune neuroinflammation with an emphasis on Tregs and Tr1 cells in MS.