Differential cytokine requirements for regulation of autoimmune gastritis and colitis by CD4(+)CD25(+) T cells

Critical influence of cytokines and immune cells in autoimmune gastritis

Gastric cancer (GC) is a type of the most common cancers. Autoimmune gastritis (AIG) and infection with Helicobacter pylori (HP) are the risk factors of triggering GC. With the emphasis on the treatment of HP, the incidence and prevalence of HP infection in population is decreasing. However, AIG lacks accurate diagnosis and treatment methods, which occupies high cancer risk factors. AIG is controlled by the immune environment of the stomach, including immune cells, inflammatory cells, and infiltrating intercellular material. Various immune cells or cytokines play a central role in the process of regulating gastric parietal cells. Abnormal expression levels of cytokines involved in immunity are bound to face the risk of tumorigenesis. Therefore, it is particularly important for preventing or treating AIG and avoiding the risk of gastric cancer to clarify the confirmed action mode of immune cells and cytokines in the gastric system. Herein, we briefly reviewed the role of the immune environment under AIG, focussing on describing these double-edged effects between immune cells and cytokines, and pointing out potential research challenges.

Anti-inflammatory effect of dental pulp stem cells

Dental pulp stem cells (DPSCs) have received a lot of attention as a regenerative medicine tool with strong immunomodulatory capabilities. The excessive inflammatory response involves a variety of immune cells, cytokines, and has a considerable impact on tissue regeneration. The use of DPSCs for controlling inflammation for the purpose of treating inflammation-related diseases and autoimmune disorders such as supraspinal nerve inflammation, inflammation of the pulmonary airways, systemic lupus erythematosus, and diabetes mellitus is likely to be safer and more regenerative than traditional medicines. The mechanism of the anti-inflammatory and immunomodulatory effects of DPSCs is relatively complex, and it may be that they themselves or some of the substances they secrete regulate a variety of immune cells through inflammatory immune-related signaling pathways. Most of the current studies are still at the laboratory cellular level and animal model level, and it is believed that through the efforts of more researchers, DPSCs/SHED are expected to be transformed into excellent drugs for the clinical treatment of related diseases.

Mitigation of DSS-Induced Colitis Potentially via Th1/Th2 Cytokine and Immunological Function Balance Induced by Phenolic-Enriched Buckwheat (Fagopyrum esculentum Moench) Bee Pollen Extract

Colitis is an inflammatory disease that results from the overactivation of effector immune cells, producing a high quantity of pro-inflammatory cytokines. Our study aimed to explore whether buckwheat (F. esculentum) bee pollen extract (FBPE) could inhibit the progression of dextran sulfate sodium (DSS)-induced colitis via regulating immune function. We isolated and identified six main phenolic compounds of FBPE such as luteolin (9.46 mg/g) by column chromatography, HPLC-DAD, ESI-MS and NMR spectroscopy, then assessed their effects on colonic mucosal injury by clinical symptoms, histomorphology and immunohistochemistry examinations. The results showed that FBPE at 25.2 g/kg body weight (g/kg BW) changed the clinical symptoms of colitis, the ICAM-1 expression in colon, the activity of related inflammatory mediators in colon tissue and helped restore the immune system. Compared with the model group (40.28%), the CD4 positivity was significantly reduced in the HD (High-dose group: 25.2 g FBPE/kg BW/day) group (20.45%). Administration of 25.2 g/kg BW of FBPE decreased the IFN-γ, TNF-α and IL-4 levels, while enhancing the IL-10 level, and significantly inhibited the abnormally decreased IgG (Model: 13.25 mg/mL, HD: 14.06 mg/mL), showing a reversal effect on the Th1/Th2 levels in colitis. These findings suggested that FBPE at 25.2 g/kg BW had the effects of alleviating colitis and immunomodulation, which can help in the development of safe and effective immune therapy.

Immunological findings in patients with migraine and other primary headaches: a narrative review

Experimental findings suggest an involvement of neuroinflammatory mechanisms in the pathophysiology of migraine. Specifically, preclinical models of migraine have emphasized the role of neuroinflammation following the activation of the trigeminal pathway at several peripheral and central sites including dural vessels, the trigeminal ganglion, and the trigeminal nucleus caudalis. The evidence of an induction of inflammatory events in migraine pathophysiological mechanisms has prompted researchers to investigate the human leukocyte antigen (HLA) phenotypes as well as cytokine genetic polymorphisms in order to verify their potential relationship with migraine risk and severity. Furthermore, the role of neuroinflammation in migraine seems to be supported by evidence of an increase in pro-inflammatory cytokines, both ictally and interictally, together with the prevalence of Th1 lymphocytes and a reduction in regulatory lymphocyte subsets in peripheral blood of migraineurs. Cytokine profiles of cluster headache (CH) patients and those of tension-type headache patients further suggest an immunological dysregulation in the pathophysiology of these primary headaches, although evidence is weaker than for migraine. The present review summarizes available findings to date from genetic and biomarker studies that have explored the role of inflammation in primary headaches.

Nigella sativa in controlling Type 2 diabetes, cardiovascular, and rheumatoid arthritis diseases: Molecular aspects

Oxidative stress is an important factor in the etiology of several chronic diseases that include cardiovascular disease (CVD), Type 2 diabetes (T2D), and rheumatoid arthritis (RA). Oxidative stress can lead to inflammation, and this can contribute to these chronic diseases. Reducing inflammation and oxidative stress may, therefore, be useful in the prevention and treatment of these conditions. One of the treatment options for chronic diseases is the use of traditional medicine and herbs, such as Nigella sativa. This is one of the herbs that have recently been assessed for its ability to reduce inflammation and oxidative stress. We have reviewed the reported effects of N. sativa on risk factors of chronic diseases (CVD, DM, and RA) with emphasis on molecular and cellular mechanisms in controlling inflammation and oxidative stress. Various mechanisms have been proposed to contribute to the beneficial properties of N. sativa, including a reduction of lipid peroxidation via its antioxidant properties; agonist of peroxisome proliferator-activated receptor gamma in adipose tissue; activation of AMP-activated protein kinase, increased antioxidants, inhibition of nuclear factor-kappa B pathway; increased in interleukin-10 expression, CD4+ T-cell percentage, T regulatory cell percentage (CD4+ CD25+ T-cell) in peripheral blood, and CD4+/CD8+ ratio, but to prove this claim, it is necessary to conduct experimental and well-designed clinical trial studies with a larger sample size on the effects of N. sativa on these chronic diseases.

The Pungent and Hot Chinese Herbs Cause Heat Syndrome in Rats by Affecting the Regulatory T Cells

Heat syndrome is a folk saying in China, which is used to describe people with symptoms such as aphtha, oral ulcer, glossitis, swelling and aching of gingiva, and dry eye. Aconitum carmichaelii Debx. (A), Zingiber officinale Rosc. (Z), and Cinnamomum cassia Presl (C) are the representatives of pungent and hot Chinese herbs which may cause heat syndrome. In order to explore the mechanism of pungent herbs-induced heat syndrome, rats were treated with AZC extracts at different concentrations and at different time periods. A series of cytokines were determined using the cytokine antibody array; some immunosuppressive cytokines, including TGF-β, IL-10, and IL-35, significantly increased in AZC group as compared with control group. Higher mRNA expressions of Foxp3, TGF-β, IL-10, and IL-35 were found in the spleen and thymus of rats after treatment for 18 days based on RT-PCR. Flow cytometry result revealed that the percentage of CD4⁺CD25⁺ Treg cells and Foxp3⁺CD4⁺CD25⁺ Treg cells in spleen lymphocytes showed an increasing trend from the 3^rd day to the 18^th day after treatment with middle dose of AZC extracts. It is speculated that extracts of AZC herbs may affect the development of heat syndrome by influencing Treg cells and immunosuppressive cytokines.

Induction of PIR-A/B+ DCs in the in vitro inflammatory condition and their immunoregulatory function

BACKGROUND

Dendritic cells (DCs), primary antigen-presenting cells, are now well known as an immunoregulator of many aspects of immune responses including inflammatory bowel diseases (IBDs) such as Crohn's disease and ulcerative colitis. We have reported that PIR-A/B^high cDCs (conventional DCs) appeared in dextran sodium sulfate (DSS)-induced colitis and serve as a negative immunoregulator in an animal model of IBD. The immunoregulatory role of PIR-A/B⁺ cDCs was confirmed in both an in vitro culture system and an in vivo transfer experiment. Here, we have investigated the differentiation process of PIR-A/B⁺ cDCs in an in vitro inflammatory environment and examined their functions.

METHODS

cDCs were isolated from the large intestinal lamina propria from C57BL/6 mice and cultured in an inflammatory environment (IL-1, IL-6, TNFα, and LPS). The appearance of PIR-A/B⁺ cDCs was determined after 24 h, and the in vitro-induced PIR-A/B⁺ cDCs were functionally and genetically examined.

RESULTS

PIR-A/B⁺ cDCs were detected after a 24-h culture only in the inflammatory environment, and the cells acted as a negative immunoregulator when examined in an allogenic mixed leukocyte reaction (MLR). The message level of IL-27 was highly upregulated in PIR-A/B⁺ cDCs, while that of high mobility group box 1 protein (HMGB1) was downregulated in these cells. This was well in accordance with the fact that PIR-A/B⁺ cDCs showed a suppressive function against activated T cells. We found that PIR-A/B⁺ cDCs produced IL-27, as verified by an ELISA assay, and that the inhibitory effect by PIR-A/B⁺ cDCs was, at least partially, due to IL-27. Furthermore, CD85d⁺ cells, a human counterpart of mouse PIR-A/B⁺ cDCs, were found in the lamina propria of the colon of the patients with ulcerative colitis, but not in the similar part of the non-inflammatory area of colon specimens from patients with colon cancer.

CONCLUSIONS

PIR-A/B⁺ cDCs induced in an in vitro inflammatory environment model showed a suppressive function against activated T cells by producing an inhibitory cytokine.

CD4+CD25-Foxp3+ T cells as a marker of disease activity and organ damage in systemic lupus erythematosus patients

INTRODUCTION

T regulatory cells (Treg) play an important role in the maintenance of immune cell homeostasis, as it has been reported that CD4+CD25+ T cells suppress the auto-reactive responses in autoimmune diseases such as systemic lupus erythematosus (SLE). The clinical significance of the recently identified population of CD4+CD25-Foxp3+ T cells and whether they are associated with particular organ involvement is still not clear. So, the aim of our study was to evaluate the presence of CD4+CD25-Foxp3+ cells in SLE patients in comparison to healthy controls and to determine whether their frequency is associated with disease activity and particular clinical manifestations in these SLE patients.

MATERIAL AND METHODS

The frequency of CD4+CD25-Foxp3+ T cells was analyzed in 56 female SLE patients and 30 healthy female control subjects, using flow cytometry (FACS). CD4+CD25-Foxp3+ T cells were correlated with clinical and laboratory data and the SLE Disease Activity Index (SLEDAI).

RESULTS

The level of CD4+CD25-Foxp3+ T cells was significantly increased in SLE patients (15.57 ±4.32%) as compared with the control group (2.46 ±0.65%). A significant correlation was observed for the percentage of CD4+CD25-Foxp3+ T cells with clinical disease activity scores and disease duration (r = 0.6, p < 0.001; r = 0.3, p = 0.02 respectively). It was also positively correlated with renal impairment and hematological involvement.

CONCLUSIONS

Systemic lupus erythematosus patients exhibited an altered level of their CD4+Foxp3+ T cells with increased levels of CD4+CD25-Foxp3+ cells.

Role of the T and B lymphocytes in pathogenesis of autoimmune thyroid diseases

Autoimmune thyroid disorders (AITD) broadly include Graves' disease and Hashimoto's thyroiditis which are the most common causes of thyroid gland dysfunctions. These disorders develop due to complex interactions between environmental and genetic factors and are characterized by reactivity to self-thyroid antigens due to autoreactive lymphocytes escaping tolerance. Both cell-mediated and humoral responses lead to tissue injury in autoimmune thyroid disease. The differentiation of CD4+ cells in the specific setting of immune mediators (for example cytokines, chemokines) results in differentiation of various T cell subsets. T cell identification has shown a mixed pattern of cytokine production indicating that both subtypes of T helper, Th1 and Th2, responses are involved in all types of AITD. Furthermore, recent studies described T cell subtypes Th17 and Treg which also play an essential role in pathogenesis of AITD. This review will focus on the role of the T regulatory (Treg) and T helper (Th) (especially Th17) lymphocytes, and also of B lymphocytes in AITD pathogenesis. However, we have much more to learn about cellular mechanisms and interactions in AITD before we can develop complete understanding of AITD pathophysiology.

IL-4 enhances IL-10 production in Th1 cells: implications for Th1 and Th2 regulation

IL-10 is an immunomodulatory cytokine with a critical role in limiting inflammation in immune-mediated pathologies. The mechanisms leading to IL-10 expression by CD4⁺ T cells are being elucidated, with several cytokines implicated. We explored the effect of IL-4 on the natural phenomenon of IL-10 production by a chronically stimulated antigen-specific population of differentiated Th1 cells. In vitro, IL-4 blockade inhibited while addition of exogenous IL-4 to Th1 cultures enhanced IL-10 production. In the in vivo setting of peptide immunotherapy leading to a chronically stimulated Th1 phenotype, lack of IL-4Rα inhibited the induction of IL-10. Exploring the interplay of Th1 and Th2 cells through co-culture, Th2-derived IL-4 promoted IL-10 expression by Th1 cultures, reducing their pathogenicity in vivo. Co-culture led to upregulated c-Maf expression with no decrease in the proportion of T-bet⁺ cells in these cultures. Addition of IL-4 also reduced the encephalitogenic capacity of Th1 cultures. These data demonstrate that IL-4 contributes to IL-10 production and that Th2 cells modulate Th1 cultures towards a self-regulatory phenotype, contributing to the cross-regulation of Th1 and Th2 cells. These findings are important in the context of Th1 driven diseases since they reveal how the Th1 phenotype and function can be modulated by IL-4.

Contributions of the intestinal microbiome in lung immunity

The intestine is a critical site of immune cell development that not only controls intestinal immunity but extra-intestinal immunity as well. Recent findings have highlighted important roles for gut microbiota in shaping lung inflammation. Here, we discuss interactions between the microbiota and immune system including T cells, protective effects of microbiota on lung infections, the role of diet in shaping the composition of gut microbiota and susceptibility to asthma, epidemiologic evidence implicating antibiotic use and microbiota in asthma and clinical trials investigating probiotics as potential treatments for atopy and asthma. The systemic effects of gut microbiota are partially attributed to their generating metabolites including short chain fatty acids, which can suppress lung inflammation through the activation of G protein-coupled receptors. Thus, studying the interactions between microbiota and immune cells can lead to the identification of therapeutic targets for chronic lower respiratory diseases.

Therapeutic immune monitoring of CD4+CD25+ T cells in chronic myeloid leukemia patients treated with tyrosine kinase inhibitors

Tyrosine kinase inhibitors (TKIs), including imatinib, dasatinib and nilotinib, are effective forms of therapy for various types of solid cancers and Philadelphia chromosome-positive (Ph⁺) chronic myeloid leukemia. A number of TKIs have been known to have strong effects on T cells, particularly cluster of differentiation (CD) 4⁺CD25⁺ T cells, also known as regulatory T cells (Tregs). There is currently a deficit in the available clinical data regarding this area of study. In the present study, a total of 108 peripheral blood samples were collected from patients with chronic myeloid leukemia (CML) at diagnosis (n=31), and at 3 and 6 months following treatment with TKI [imatinib (n=12), dasatinib (n=11) and nilotinib groups (n=8)] and healthy controls (n=15). Peripheral blood mononuclear cells were collected from the patients prior to and following TKI treatment. The subtype and number of T lymphocytes in patients and healthy donors were analyzed using flow cytometry. Additionally, flow cytometry and ELISA were used to detect the proliferation and suppression of Tregs. Expression of cytokines and other molecules [forkhead box P3 (FOXP3), glucocorticoid-induced tumor necrosis factor receptor (GITR) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4)] were also analyzed at 3 and 6 months following treatment with TKIs. It was indicated that, at diagnosis, a similar number of lymphocytes were detected in patients and control. However, following treatment with a TKI, the number of total T cells, Tregs, CD4⁺ T and CD8⁺ T cells decreased to various degrees in patients. Furthermore, the decrease in the number of Tregs was more significant with time. Although treatment with imatinib, dasatinib and nilotinib demonstrated similar inhibitory effects on the quantity of Tregs in vivo, the TKIs exhibited differential effects on the function of Tregs in vitro. Proliferation, suppression and expression of cytokines [interleukin (IL)-4, IL-10 and transforming growth factor (TGF)-β] and molecules (FOXP3, GITR and CTLA-4) decreased significantly in treatment groups with imatinib and dasatinib. The decrease was not significant in the nilotinib treatment group. Imatinib and dasatinib may exert more marked inhibitory roles compared with nilotinib on regulating the number and function of Tregs. These results suggest that personalized treatment and follow-up of CML patients during TKI treatment, particularly for those who received post-transplant TKI treatment may be beneficial.

Increased CD4+CD45RA-FoxP3low cells alter the balance between Treg and Th17 cells in colitis mice

AIM

To investigate the role of regulatory T cell (Treg) subsets in the balance between Treg and T helper 17 (Th17) cells in various tissues from mice with dextran sulfate sodium-induced colitis.

METHODS

Treg cells, Treg cell subsets, Th17 cells, and CD4⁺CD25⁺FoxP3⁺IL-17⁺ cells from the lamina propria of colon (LPC) and other ulcerative colitis (UC) mouse tissues were evaluated by flow cytometry. Forkhead box protein 3 (FoxP3), interleukin 17A (IL-17A), and RORC mRNA levels were assessed by real-time PCR, while interleukin-10 (IL-10) and IL-17A levels were detected with a Cytometric Beads Array.

RESULTS

In peripheral blood monocytes (PBMC), mesenteric lymph node (MLN), lamina propria of jejunum (LPJ) and LPC from UC mice, Treg cell numbers were increased (P < 0.05), and FoxP3 and IL-10 mRNA levels were decreased. Th17 cell numbers were also increased in PBMC and LPC, as were IL-17A levels in PBMC, LPJ, and serum. The number of FrI subset cells (CD4⁺CD45RA⁺FoxP3^low) was increased in the spleen, MLN, LPJ, and LPC. FrII subset cells (CD4⁺CD45RA^-FoxP3^high) were decreased among PBMC, MLN, LPJ, and LPC, but the number of FrIII cells (CD4⁺CD45RA^-FoxP3^low) and CD4⁺CD25⁺FoxP3⁺IL-17A⁺ cells was increased. FoxP3 mRNA levels in CD4⁺CD45RA^-FoxP3^low cells decreased in PBMC, MLN, LPJ, and LPC in UC mice, while IL-17A and RORC mRNA increased. In UC mice the distribution of Treg, Th17 cells, CD4⁺CD45RA^-FoxP3^high, and CD4⁺CD45RA^-FoxP3^low cells was higher in LPC relative to other tissues.

CONCLUSION

Increased numbers of CD4⁺CD45RA^-FoxP3^low cells may cause an imbalance between Treg and Th17 cells that is mainly localized to the LPC rather than secondary lymphoid tissues.

In vivo induction of regulatory T cells for immune tolerance in hemophilia

Current therapy for the X-linked coagulation disorder hemophilia is based on intravenous infusion of the specifically deficient coagulation factor. However, 20-30% of hemophilia A patients (factor VIII, FVIII, deficiency) generate inhibitory antibodies against FVIII. While formation of inhibitors directed against factor IX, FIX, resulting from hemophilia B treatment is comparatively rare, a serious complication that is often associated with additional immunotoxicities, e.g. anaphylaxis, occurs. Current immune tolerance protocols to eradiate inhibitors are lengthy, expensive, not effective in all patients, and there are no prophylactic tolerance regimens to prevent inhibitor formation. The outcomes of recent experiments in animal models of hemophilia demonstrate that regulatory CD4(+) T cells (Treg) are of paramount importance in controlling B cell responses to FVIII and FIX. This article reviews several novel strategies designed to in vivo induce coagulation factor-specific Treg cells and discusses the subsets of Treg that may promote immune tolerance in hemophilia. Among others, drug- and gene transfer-based protocols, lymphocyte transplant, and oral tolerance are reviewed.

Manipulation of regulatory T cells and antigen-specific cytotoxic T lymphocyte-based tumour immunotherapy

The most potent killing machinery in our immune system is the cytotoxic T lymphocyte (CTL). Since the possibility for self-destruction by these cells is high, many regulatory activities exist to prevent autoimmune destruction by these cells. A tumour (cancer) grows from the cells of the body and is tolerated by the body's immune system. Yet, it has been possible to generate tumour-associated antigen (TAA) -specific CTL that are also self-antigen specific in vivo, to achieve a degree of therapeutic efficacy. Tumour-associated antigen-specific T-cell tolerance through pathways of self-tolerance generation represents a significant challenge to successful immunotherapy. CD4(+)  CD25(+)  FoxP3(+) T cells, referred to as T regulatory (Treg) cells, are selected in the thymus as controllers of the anti-self repertoire. These cells are referred to as natural T regulatory (nTreg) cells. According to the new consensus (Nature Immunology 2013; 14:307-308) these cells are to be termed as (tTreg). There is another class of CD4(+) Treg cells also involved in regulatory function in the periphery, also phenotypically CD4(+)  CD25(±) , classified as induced Treg (iTreg) cells. These cells are to be termed as peripherally induced Treg (pTreg) cells. In vitro-induced Treg cells with suppressor function should be termed as iTreg. These different Treg cells differ in their requirements for activation and in their mode of action. The current challenges are to determine the degree of specificity of these Treg cells in recognizing the same TAA as the CTL population and to circumvent their regulatory constraints so as to achieve robust CTL responses against cancer.

Helicobacter pylori cag pathogenicity island's role in B7-H1 induction and immune evasion

During Helicobacter pylori (H. pylori) infection CD4⁺ T cells in the gastric lamina propria are hyporesponsive and polarized by Th1/Th17 cell responses controlled by T_reg cells. We have previously shown that H. pylori upregulates B7-H1 expression on GEC, which, in turn, suppress T cell proliferation, effector function, and induce T_reg cells in vitro. In this study, we investigated the underlying mechanisms and the functional relevance of B7-H1 induction by H. pylori infection to chronic infection. Using H. pylori wild type (WT), cag pathogenicity island (cag PAI^-) and cagA^- isogenic mutant strains we demonstrated that H. pylori requires its type 4 secretion system (T4SS) as well as its effector protein CagA and peptidoglycan (PG) fragments for B7-H1 upregulation on GEC. Our study also showed that H. pylori uses the p38 MAPK pathway to upregulate B7-H1 expression in GEC. In vivo confirmation was obtained when infection of C57BL/6 mice with H. pylori PMSS1 strain, which has a functional T4SS delivery system, but not with H. pylori SS1 strain lacking a functional T4SS, led to a strong upregulation of B7-H1 expression in the gastric mucosa, increased bacterial load, induction of T_reg cells in the stomach, increased IL-10 in the serum. Interestingly, B7-H1^-/- mice showed less T_reg cells and reduced bacterial loads after infection. These studies demonstrate how H. pylori T4SS components activate the p38 MAPK pathway, upregulate B7-H1 expression by GEC, and cause T_reg cell induction; thus, contribute to establishing a persistent infection characteristic of H. pylori.

Levels of interleukin-35 and its relationship with regulatory T-cells in chronic hepatitis B patients

Interleukin-35 is a novel inhibition cytokine secreted by CD4+CD25+ regulatory T-cells (Treg) in murine. However, it is disputed whether IL-35 could be secreted by Treg cells in humans. In this study, the levels of IL-35 were detected, and its relationship with regulatory T-cells in chronic hepatitis B (CHB) patients was investigated. It was shown that the levels of IL-35 in CHB patients were higher than those in normal controls, and the levels increased gradually, accompanied with the severe liver inflammation and necrosis and poor synthesis function. Treg cells may secrete IL-35, whose levels would become higher, accompanied by a longer activated time. Thus, IL-35 as a cytokine secreted by Treg cells may accelerate liver inflammation and necrosis, and inhibit the synthesis function.

Glycogen synthase kinase-3 controls IL-10 expression in CD4(+) effector T-cell subsets through epigenetic modification of the IL-10 promoter

The serine/threonine kinase glycogen synthase kinase-3 (GSK3) plays an important role in balancing pro- and anti-inflammatory cytokines. We have examined the role of GSK3 in production of IL-10 by subsets of CD4⁺ T helper cells. Treatment of naive murine CD4⁺ T cells with GSK3 inhibitors did not affect their production of IL-10. However, treatment of Th1 and Th2 cells with GSK3 inhibitors dramatically increased production of IL-10. GSK3 inhibition also led to upregulation of IL-10 among Th1, Th2, and Th17 subsets isolated from human blood. The encephalitogenic potential of GSK3 inhibitor treated murine Th1 cells was significantly reduced in adoptive transfer experiments by an IL-10-dependent mechanism. Analysis of the murine IL-10 promoter in response to inhibition of GSK3 in Th1 cells showed modification to a transcriptionally active state indicated by changes in histone H3 acetylation and methylation. Additionally, GSK3 inhibition increased expression of the transcription factors c-Maf, Nfil3, and GATA3, correlating with the increase in IL-10. These findings are important in the context of autoimmune disease since they show that it is possible to reprogram disease-causing cells through GSK3 inhibition.

Increased production of interleukin-17 over interleukin-10 by treg cells implicates inducible costimulator molecule in experimental spondyloarthritis

OBJECTIVE

HLA-B27/human β2 -microglobulin (hβ2 m)-transgenic (B27-transgenic) rats develop an inflammatory disorder resembling spondyloarthritis, with accumulation of proinflammatory Th17 cells. Because Treg cells and Th17 cells have opposing effects in inflammatory disorders, we sought to determine whether biased expansion of Th17 cells could result from altered Treg cell frequency and/or function in B27-transgenic rats.

METHODS

We characterized the phenotype and function of Treg cells from B27-transgenic rats in comparison with those from control rats, by examining their expression of cell surface markers, suppressive activity, cytokine production, and differentiation pattern.

RESULTS

In B27-transgenic rats, the preferential accumulation of CD4+ Teff cells over Treg cells was not associated with a defect in Treg cell differentiation or suppressive activity. The expression of Treg cell markers was similar between B27-transgenic and control rats, with the exception of the inducible costimulator (ICOS) molecule, which was overexpressed in B27-transgenic rats. High levels of ICOS are considered to be a hallmark of Treg cells with heightened suppressive activity and interleukin-10 (IL-10) expression. Paradoxically, the production of IL-10 by Treg cells was reduced in B27-transgenic rats, whereas the production of IL-17 was enhanced. Moreover, the addition of anti-ICOS monoclonal antibodies during Treg cell differentiation in the presence of dendritic cells from B27-transgenic rats reversed this cytokine profile, restoring the balance between IL-10 and IL-17 in Treg cells from B27-transgenic rats.

CONCLUSION

We observed dysregulated production of IL-10 and IL-17 by Treg cells from B27-transgenic rats, which may contribute to disease development. Moreover, our data highlight a key role for ICOS signaling in the generation of imbalanced production of IL-10 and IL-17 by Treg cells in this experimental model of spondyloarthritis.

Immunoregulatory function of PIR-A/B+ DCs in the inflammatory responses of dextran sodium sulfate-induced colitis

BACKGROUND

Dendritic cells (DCs) may play an important role in forms of inflammatory bowel disease (IBD), such as Crohn's disease and ulcerative colitis. DCs are generally recognized as initiators of acquired immunity and also serve as regulators of both innate and acquired immunity. We used the animal model of colitis induced by dextran sodium sulfate (DSS), and examined whether DCs prepared from the colon show immunoregulatory roles in the termination of DSS-induced colitis.

METHODS

C57BL/6 mice exposed to DSS for 5 days developed acute colitis. DCs were isolated from the large intestinal lamina propria, and then analyzed for phenotypical, functional, and genetic data.

RESULTS

Only PIR-A/B(low) conventional DCs (cDCs) were detected in the steady state. However, after the treatment of DSS, PIR-A/B(high) cDCs appeared and gradually increased from day 5 to day 7, at which time the DSS-induced colitis was terminated. Then, allogeneic mixed leukocyte reaction (MLR) was performed. The stimulatory activity of PIR-A/B(high) cDCs obtained on day 7 was very low, and the addition of PIR-A/B(high) cDCs suppressed the T cell proliferation in MLR, indicating the immunoregulatory role of PIR-A/B(high) cDCs. The immunoregulatory role of PIR-A/B(high) cDCs was confirmed by the in vivo transfer experiment, showing their therapeutic effect on DSS-induced colitis. The message level of TGFβi was significantly higher in PIR-A/B(high) cDCs, while that of IFN-γ was highly upregulated in PIR-A/B(low) cDCs, being well in accordance with the fact that PIR-A/B(high) cDCs showed a suppressive function against activated T cells.

CONCLUSION

PIR-A/B(high) cDCs showed a suppressive function against activated T cells by producing inhibitory cytokines.

Active players in resolution of shock/sepsis induced indirect lung injury: immunomodulatory effects of Tregs and PD-1

The immunomodulatory effects of PD-1 and CD4(+)CD25(+) Tregs in the resolution of ALI are still poorly understood. Accordingly, 1 million Tregs were isolated from spleens of WT C57BL/6 or PD-1(-/-) mice (magnetical bead purification and subsequent labeling with/without Vybrant dye) and then AT into mice subjected to Hem shock during their resuscitation period, which were subsequently subjected to CLP/septic challenge (24 h post-Hem) to induce iALI. Initially, we demonstrated that Vybrant-labeled AT Tregs appear in the lungs of iALI mice. Subsequently, we found that AT of WT Tregs induced a significant repression of the indices of lung injury: a reduction of neutrophil influx to the lung tissue and a decrease of lung apoptosis compared with vehicle-treated iALI mice. In addition, these mice had substantially higher concentrations of BALF and lung-tissue IL-10 but significantly decreased levels of lung KC. However, these beneficial effects of the AT of Tregs were lost with the administration of PD-1(-/-) mouse Tregs to the recipient WT mice. ALI was exacerbated in these recipient mice receiving AT PD-1(-/-) Tregs to the same extent as iALI mice that did not receive Tregs. These data imply that Tregs can act directly to modify the innate immune response induced by experimental iALI, and this is mediated, in part, by PD-1. Hence, the manipulation of Tregs may represent a plausible target for treating iALI.

CD28/CTLA-4/B7 and CD40/CD40L costimulation and activation of regulatory T cells

Costimulatory signals are crucial for T cell activation. Attempts to block costimulatory pathways have been effective in preventing unwanted immune reactions. In particular, blocking the CD28/cytotoxic T lymphocyte antigen (CTLA)-4/B7 interaction (using CTLA-4Ig) and the CD40/CD40L interaction (using anti-CD40L antibodies) prevents T cell mediated autoimmune diseases, transplant rejection and graft vs host disease in experimental models. Moreover, CTLA-4Ig is in clinical use to treat rheumatoid arthritis (abatacept) and to prevent rejection of renal transplants (belatacept). Under certain experimental conditions, this treatment can even result in tolerance. Surprisingly, the underlying mechanisms of immune modulation are still not completely understood. We here discuss the evidence that costimulation blockade differentially affects effector T cells (Teff) and regulatory T cells (Treg). The latter are required to control inappropriate and unwanted immune responses, and their activity often contributes to tolerance induction and maintenance. Unfortunately, our knowledge on the costimulatory requirements of Treg cells is very limited. We therefore summarize the current understanding of the costimulatory requirements of Treg cells, and elaborate on the effect of anti-CD40L antibody and CTLA-4Ig treatment on Treg cell activity. In this context, we point out that the outcome of a treatment aiming at blocking the CD28/CTLA-4/B7 costimulatory interaction can vary with dosing, timing and underlying immunopathology.

CD4⁺CD25⁻Foxp3⁺ T cells: a marker for lupus nephritis?

INTRODUCTION

Systemic lupus erythematosus (SLE) is a heterogenous autoimmune disease, which can affect different organs. Increased proportions of CD4⁺CD25-Foxp3⁺ T cells have been described in SLE patients. The exact role of this cell population in SLE patients still remains unclear. We therefore analyzed this T cell subset in a large cohort of SLE patients with different organ manifestations.

METHODS

Phenotypic analyses, proportions and absolute cell numbers of CD4⁺CD25-Foxp3⁺ T cells were determined by flow cytometry (FACS) in healthy controls (HC) (n = 36) and SLE patients (n = 61) with different organ manifestations. CD4⁺CD25⁻Foxp3⁺ T cells were correlated with clinical data, the immunosuppressive therapy and different disease activity indices. In patients with active glomerulonephritis, CD4⁺CD25⁻Foxp3⁺ T cells were analyzed in urine sediment samples. Time course analyses of CD4⁺CD25⁻Foxp3⁺ T cells were performed in patients with active disease activity before and after treatment with cyclophosphamide and prednisone.

RESULTS

CD4⁺CD25⁻Foxp3⁺ T cells were significantly increased in active SLE patients and the majority expressed Helios. Detailed analysis of this patient cohort revealed increased proportions of CD4⁺CD25⁻Foxp3⁺ T cells in SLE patients with renal involvement. CD4⁺CD25⁻Foxp3⁺ T cells were also detected in urine sediment samples of patients with active glomerulonephritis and correlated with the extent of proteinuria.

CONCLUSION

CD4⁺CD25⁻Foxp3⁺ T cells resemble regulatory rather than activated T cells. Comparative analysis of CD4⁺CD25⁻Foxp3⁺ T cells in SLE patients revealed a significant association of this newly described cell population with active nephritis. Therefore CD4⁺CD25⁻Foxp3⁺ T cells might serve as an important tool to recognize and monitor SLE patients with renal involvement.

Regulation of adaptive immunity; the role of interleukin-10

Since the discovery of interleukin-10 (IL-10) in the 1980s, a large body of work has led to its recognition as a pleiotropic immunomodulatory cytokine that affects both the innate and adaptive immune systems. IL-10 is produced by a wide range of cell types, but for the purposes of this review we shall focus on IL-10 secreted by CD4(+) T cells. Here we describe the importance of IL-10 as a mediator of suppression used by both FoxP3(+) and FoxP3(-) T regulatory cells. Moreover, we discuss the molecular events leading to the induction of IL-10 secretion in T helper cell subsets, where it acts as a pivotal negative feedback mechanism. Finally we discuss how a greater understanding of this principle has allowed for the design of more efficient, antigen-specific immunotherapy strategies to exploit this natural phenomenon clinically.

Intratracheal transplantation of bone marrow-derived mesenchymal stem cells reduced airway inflammation and up-regulated CD4⁺CD25⁺ regulatory T cells in asthmatic mouse

Mesenchymal stem cells attenuate the severity of lung injury due to their immunomodulatory properties. The effect of bone marrow-derived mesenchymal stem cells on asthma is seldom reported. We have examined the effect of BMSCs on airway inflammation in asthma. Forty female BALB/c mice were equally randomised into PBS group, BMSCs treatment group, BMSCs control group and asthmatic group. Reactivity of the airway to acetylcholine was measured by barometric plethysmography. Cytokine profiles of bronchoalveolar lavage fluid and serum were determined by enzyme-linked immunosorbent assay. Morphometric analysis was done with haematoxylin and periodic-acid Schiff staining. Engraftment of BMSCs in asthmatic mice significantly decreased the number of eosinophils and mononuclear cells in bronchoalveolar lavage fluid and the airway (P < 0.05). Both goblet cell hyperplasia and responsiveness to acetylcholine were significantly reduced in BMSCs treatment groups. Moreover, BMSCs engraftment caused significant increases the ratio of Treg in pulmonary lymph node and interleukin-10 (IL-10) and interleukin-12 levels in BALF and serum. We conclude that BMSCs engraftment ameliorated airway inflammation and improved lung function in asthmatic mouse and the protective effect might be mediated by upregulating Treg and partly involved with increasing IL-10.

DNA methylation impairs TLR9 induced Foxp3 expression by attenuating IRF-7 binding activity in fulminant type 1 diabetes

Fulminant type 1 diabetes (FT1D) is an extremely aggressive disease characterized by the abrupt onset of insulin-deficient hyperglycemia. However, the precise mechanisms underlying disease etiology almost remain unclear. As mice deficient in regulatory T cells (Tregs) are prone to the development of an FT1D-like phenotype, we thus investigated whether FT1D patients manifest Treg deficiency and explored the related mechanisms. We first noted a significant reduction for Foxp3 and CTLA4 expression levels in PBMCs of FT1D patients. IRF-7 was found to selectively bind to the Foxp3 promoter, and by which it promotes Foxp3 transcription. Therefore, ectopic IRF-7 expression significantly promoted Foxp3 and CTLA4 expression in PBMCs, while knockdown of IRF-7 manifested opposite effect. Importantly, stimulation of PBMCs with CpG ODN, a ligand for TLR9, significantly induced Foxp3 expression, demonstrating that TLR9 signaling positively regulates Treg development. However, knockdown of IRF-7 expression almost completely diminished the enhancing effect of TLR9 signaling on Foxp3 expression, suggesting that IRF-7 is a downstream molecule of TLR9 signaling and is essential for TLR9 induced Treg generation. Of interestingly note, the Foxp3 promoter in FT1D patients was hypermethylated, indicating that DNA methylation could be a causative factor responsible for the reduced Foxp3 expression in FT1D patients. Indeed, our mechanistic studies revealed that DNA methylation blocked IRF-7 binding to the Foxp3 promoter. Together, our data support the notion that environmental insults in genetic predisposed subjects trigger Foxp3 promoter hypermethylation, which then prevents IRF-7 binding to the Foxp3 promoter and impairs Treg development/functionality contributing to the pathogenesis of FT1D.

Working out mechanisms of controlled/physiologic inflammation in the GI tract

The mucosal immune system is distinct from its systemic counterpart by virtue of its enormous antigenic exposure (commensal flora, food antigen, pathogens). Despite this, the mucosal immune system maintains a response defined as controlled or physiologic inflammation. This is regulated by many different mechanisms, among which there are physical, cellular and soluble factors. Our laboratory has focused on unique Tregs in the gut controlled by, in one instance, intestinal epithelial cells that serve as non-professional antigen-presenting cells. We believe that intestinal epithelial cells, expressing classical and non-classical MHC molecules, serve to activate Tregs and thus maintain controlled or physiologic inflammation. In this review, we describe regulatory cytokines and T cells that are one part of the emphasis of our laboratory.

HSP70 enhances immunosuppressive function of CD4(+)CD25(+)FoxP3(+) T regulatory cells and cytotoxicity in CD4(+)CD25(-) T cells

Human CD4⁺CD25⁺FoxP3⁺ T regulatory cells (Tregs) control effector T cells and play a central role in peripheral tolerance and immune homeostasis. Heat shock protein 70 (HSP70) is a major immunomodulatory molecule, but its effect on the functions of Tregs is not well understood. To investigate target-dependent and –independent Treg functions, we studied cytokine expression, regulation of proliferation and cytotoxicity after exposure of Tregs to HSP70. HSP70-treated Tregs significantly inhibited proliferation of CD4⁺CD25⁻ target cells and downregulated the secretion of the proinflammatory cytokines IFN-γ and TNF-α. By contrast, HSP70 increased the secretion of Treg suppressor cytokines IL-10 and TGF-β. Treatment with HSP70 enhanced the cytotoxic properties of Tregs only to a minor extent (4-fold), but led to stronger responses in CD4⁺CD25⁻ cells (42-fold). HSP70-induced modulation of T-cell responses was further enhanced by combined treatment with HSP70 plus IL-2. Treatment of Tregs with HSP70 led to phosphorylation of PI3K/AKT and the MAPKs JNK and p38, but not that of ERK1/2. Exposure of Tregs to specific inhibitors of PI3K/AKT and the MAPKs JNK and p38 reduced the immunosuppressive function of HSP70-treated Tregs as indicated by the modified secretion of specific target cell (IFN-γ, TNF-α) and suppressor cytokines (IL-10, TGF-β). Taken together, the data show that HSP70 enhances the suppressive capacity of Tregs to neutralize target immune cells. Thus HSP70-enhanced suppression of Tregs may prevent exaggerated immune responses and may play a major role in maintaining immune homeostasis.

Regulatory T lymphocytes from ALS mice suppress microglia and effector T lymphocytes through different cytokine-mediated mechanisms

Activated microglia and infiltrating lymphocytes are neuropathological hallmarks of amyotrophic lateral sclerosis (ALS), a fatal motoneuron disease. Although both cell types play pivotal roles in the ALS pathogenic process, the interactions between microglia and lymphocytes, specifically regulatory CD4+CD25High T lymphocytes (Tregs) and cytotoxic CD4+CD25- T lymphocytes (Teffs), have not been addressed. When co-cultured with mSOD1 adult microglia, mSOD1 Tregs suppressed the cytotoxic microglial factors NOX2 and iNOS through an IL-4-mediated mechanism, whereas Teffs were only minimally effective; IL-4 inhibitory antibodies blocked the suppressive function of mSOD1 Tregs, and conditioned media from mSOD1 Tregs or the addition of IL-4 reduced microglial NOX2 expression. During the stable disease phase, the total number of Tregs, specifically the numbers of CD4+CD25HighIL-4+, CD4+CD25HighIL-10+ and CD4+CD25HighTGF-β+ Tregs, were increased in ALS mice compared with WT mice; Tregs isolated during this phase reduced Teff proliferation. In contrast, during the rapidly progressing phase, the number of mSOD1 Tregs decreased while the proliferation of mSOD1 Teffs increased. The combination of IL-4, IL-10, and TGF-β was required to inhibit the proliferation of mSOD1 Teffs by mSOD1 Tregs that were isolated during the slow phase, while inhibition of mSOD1 Teffs by mSOD1 Tregs during the rapid phase, as well as WT Teffs, was not dependent on these factors. Thus, mSOD1 Tregs at the slow phase suppressed microglial toxicity and SOD1 Teff proliferation through different mechanisms; microglial activation was suppressed through IL-4 whereas mSOD1 Teffs were suppressed by IL-4, IL-10 and TGF-β. These data suggest that mSOD1 Tregs contribute to the slowly progressing phase in ALS mice and may offer a novel therapeutic option for ALS patients.

Adoptive transfer with in vitro expanded human regulatory T cells protects against porcine islet xenograft rejection via interleukin-10 in humanized mice

T cell-mediated rejection remains a barrier to the clinical application of islet xenotransplantation. Regulatory T cells (Treg) regulate immune responses by suppressing effector T cells. This study aimed to determine the ability of human Treg to prevent islet xenograft rejection and the mechanism(s) involved. Neonatal porcine islet transplanted NOD-SCID IL2rγ(-/-) mice received human peripheral blood mononuclear cells (PBMC) with in vitro expanded autologous Treg in the absence or presence of anti-human interleukin-10 (IL-10) monoclonal antibody. In addition, human PBMC-reconstituted recipient mice received recombinant human IL-10 (rhIL-10). Adoptive transfer with expanded autologous Treg prevented islet xenograft rejection in human PBMC-reconstituted mice by inhibiting graft infiltration of effector cells and their function. Neutralization of human IL-10 shortened xenograft survival in mice receiving human PBMC and Treg. In addition, rhIL-10 treatment led to prolonged xenograft survival in human PBMC-reconstituted mice. This study demonstrates the ability of human Treg to prevent T-cell effector function and the importance of IL-10 in this response. In vitro Treg expansion was a simple and effective strategy for generating autologous Treg and highlighted a potential adoptive Treg cell therapy to suppress antigraft T-cell responses and reduce the requirement for immunosuppression in islet xenotransplantation.

Interleukin 10 in the tumor microenvironment: a target for anticancer immunotherapy

IL-10 is an immunomodulatory cytokine that is frequently upregulated in various types of cancer. The biological role of IL-10 in cancer is quite complex; however, the presence of IL-10 in advanced metastases and the positive correlation between serum IL-10 levels and progression of disease indicates a critical role of IL-10 in the tumor microenvironment. IL-10 has been shown to directly affect the function of antigen-presenting cells by inhibiting the expression of MHC and costimulatory molecules, which in turn induces immune suppression or tolerance. Additionally, IL-10 downregulates the expression of Th1 cytokines and induces T-regulatory responses. Taken together, a combination of IL-10 antagonism and immunostimulatory treatments such as cancer vaccines, Toll-like receptor agonists, Th1 cytokines, and chemokines would be a logical approach to enhance an antitumor immune response.

A convenient model of severe, high incidence autoimmune gastritis caused by polyclonal effector T cells and without perturbation of regulatory T cells

Autoimmune gastritis results from the breakdown of T cell tolerance to the gastric H(+)/K(+) ATPase. The gastric H(+)/K(+) ATPase is responsible for the acidification of gastric juice and consists of an α subunit (H/Kα) and a β subunit (H/Kβ). Here we show that CD4(+) T cells from H/Kα-deficient mice (H/Kα(-/-)) are highly pathogenic and autoimmune gastritis can be induced in sublethally irradiated wildtype mice by adoptive transfer of unfractionated CD4(+) T cells from H/Kα(-/-) mice. All recipient mice consistently developed the most severe form of autoimmune gastritis 8 weeks after the transfer, featuring hypertrophy of the gastric mucosa, complete depletion of the parietal and zymogenic cells, and presence of autoantibodies to H(+)/K(+) ATPase in the serum. Furthermore, we demonstrated that the disease significantly affected stomach weight and stomach pH of recipient mice. Depletion of parietal cells in this disease model required the presence of both H/Kα and H/Kβ since transfer of H/Kα(-/-) CD4(+) T cells did not result in depletion of parietal cells in H/Kα(-/-) or H/Kβ(-/-) recipient mice. The consistency of disease severity, the use of polyclonal T cells and a specific T cell response to the gastric autoantigen make this an ideal disease model for the study of many aspects of organ-specific autoimmunity including prevention and treatment of the disease.

Two modes of immune suppression by Foxp3(+) regulatory T cells under inflammatory or non-inflammatory conditions

Foxp3-expressing regulatory T cells (Tregs) play a crucial role in maintaining immune tolerance and homeostasis. One of the key issues for understanding Treg immunobiology is to determine how they suppress excessive or aberrant immune responses. Although a number of molecules have been reported to contribute to Treg suppressive function, the importance and precise role of each molecule is not clear. In this review, we propose and discuss that two modes of suppression can be distinguished. In the physiological and steady state, activation of naïve T cells can be suppressed by natural Tregs via deprivation of activation signals including CD28 signal and IL-2 from antigen-reactive T cells, keeping the latter in a naïve state in lymphoid tissues. These deprivation mechanisms are transiently abrogated in inflammatory conditions, allowing T cells to respond to antigen. In contrast, in highly inflammatory environments, for example, in microbial infection, activated Tregs acquire the capacity to kill or inactivate effector T cells and antigen-presenting cells, for example, via granzyme/perforin formation and IL-10 secretion, thereby actively damping excessive immune responses. Understanding these processes will help effectively controlling physiological and pathological immune responses via Tregs.

Porcine regulatory T cells: mechanisms and T-cell targets of suppression

Tregs are known for their suppressive capacity on various immune reactions. In swine, existence as well as suppressive activity of Foxp3(+) Tregs could be demonstrated but detailed functional investigations are lacking. Therefore, we analysed the functional properties of porcine Tregs. We observed that besides TCR stimulation Tregs require IL-2 for activation. Furthermore, we investigated the following mechanisms of suppression: (i) cell-cell contact dependency, (ii) production of soluble suppressive factors and (iii) competition for growth factors. Our experiments revealed that suppression by porcine Tregs is abrogated by blocking cell-cell contact or by supplementing excessive amounts of IL-2. Additionally it could be shown that porcine Tregs produce immunosuppressive IL-10. Thereby, we demonstrated that porcine Tregs can use all main mechanisms of suppression mentioned above. Further investigations on the suppressive activity of Tregs using CFSE proliferation assays demonstrated that suppression affects T-helper cells as well as cytotoxic T lymphocytes and TCR-γδ T cells.

Role of dendritic cell maturity/costimulation for generation, homeostasis, and suppressive activity of regulatory T cells

Tolerogenicity of dendritic cells (DCs) has initially been attributed exclusively to immature/resting stages, while mature/activated DCs were considered strictly immunogenic. Later, all different subsets among the myeloid/conventional DCs and plasmacytoid DCs have been shown to bear tolerogenic potential, so that tolerogenicity could not be attributed to a specific subset. Immunosuppressive treatments of immature DC subsets could prevent re-programming into mature DCs or upregulated inhibitory surface markers or cytokines. Furthermore, the different T cell tolerance mechanisms anergy, deletion, immune deviation, and suppression require different quantities and qualities of costimulation by DCs. Since expansion of regulatory T cells (Tregs) has been shown to be promoted best by fully mature DCs the role of CD80/B7-1 and CD86/B7-2 as major costimulatory molecules for Treg biology is under debate. In this review, we discuss the role of these and other costimulatory molecules on myeloid DCs and their ligands CD28 and CD152/CTLA-4 on Tregs for peripheral conversion from naive CD4⁺ T cells into the major subsets of Foxp3⁺ Tregs and Foxp3⁻ IL-10⁺ regulatory type-1 T cells (Tr1) or Tr1-like cells and their role for peripheral maintenance in the steady state and after activation.

Intestinal dendritic cells in the pathogenesis of inflammatory bowel disease

The gastrointestinal tract harbors a large number and diverse array of commensal bacteria and is an important entry site for pathogens. For these reasons, the intestinal immune system is uniquely dedicated to protect against infections, while avoiding the development of destructive inflammatory responses to the microbiota. Several models have been proposed to explain how the immune system discriminates between, and appropriately responds to, commensal and pathogenic microorganisms. Dendritic cells (DCs) and regulatory T cells (Treg) are instrumental in maintaining immune homeostasis and tolerance in the gut. DCs are virtually omnipresent and are remarkably plastic, having the ability to adapt to the influences of the microenvironment. Different DC populations with partially overlapping phenotypic and functional properties have been described in different anatomical locations. DCs in the draining mesenteric lymph nodes, in the intestinal lamina propria and in Peyer’s patches partake both in the control of intestinal inflammation and in the maintenance of gut tolerance. In this respect, gut-resident DCs and macrophages exert tolerogenic functions as they regularly encounter and sense commensal bacteria. In contrast, migrating DC subsets that are recruited to the gut as a result of pathogenic insults initiate immune responses. Importantly, tolerogenic DCs act by promoting the differentiation and expansion of Treg cells that efficiently modulate gut inflammation, as shown both in pre-clinical models of colitis and in patients with inflammatory bowel disease (IBD). This article reviews the phenotypic and functional features of gut DC subsets and discusses the current evidence underpinning the DC contribution to the pathogenesis of the major clinical subtypes of human IBD. It also addresses the potential clinical benefit derived from DC targeting either in vivo or in vitro.

Regulatory T cells in cutaneous immune responses

Regulatory T cells (Treg) are a subset of T cells with strong immunosuppressive activity. In the skin, it has recently been revealed that Treg play important roles not only in the maintenance of skin homeostasis but also in the regulation of the immune responses, such as contact hypersensitivity and atopic dermatitis. Furthermore, the skin plays important roles in the induction of Treg in the periphery. In this review, we will provide an overview of the mechanism of Treg-mediated immunosuppression and discuss the role of Treg in the skin.

Abrogation of Treg function deteriorates rheumatoid arthritis

An early prognostic indicator which warns of progressive joint destruction of rheumatoid arthritis (RA) was explored using a novel suspension-array technique in moderate (Steinbrocker stage I and II) and severe (Steinbrocker stage IV) RA patients. DNA microarray analysis of peripheral blood lymphocytes showed significant increase of interleukin (IL)-2 receptor α-chain (CD25) gene expression, a regulatory T cell (Treg) surface marker in severe RA patients. In contrast, suspension array, a comprehensive bead-based enzyme-linked immunosorbent assay (ELISA), revealed decreased production of IL-10 and increased production of interferon (IFN)-γ in sera in the incipient stage of the aggressive disease process. Both in moderate and in severe RA patients, the IFN-γ/IL-10 ratio indicated deterioration of the disease with universal validity. Fluorescence-activated cell sorting (FACS) and reverse-transcription polymerase chain reaction (RT-PCR) analysis showed extant CD4+CD25+ regulatory T cells in severe RA patients, however Foxp3, a regulatory T cell-specific transcription factor, gene expression was absent, while glucocorticoid-induced tumor necrosis factor (TNF) receptor family-related protein (GITR), which transmits a signal that abrogates regulatory T cell functions, was elevated. In the current study, we showed the validity of suspension-array analysis for enabling more complete understanding of RA, and showed that IFN-γ/IL-10 ratio can be a prognostic tool for early lesion and more aggressive RA.

Regulation of T cell activation by TLR ligands

Regulatory T cells (Treg) maintain peripheral tolerance and play a critical role in the control of the immune response in infection, tumor defense, organ transplantation and allergy. CD4(+)CD25(high) Treg suppress the proliferation and cytokine production of CD4(+)CD25(-) responder T cells. The suppression requires cell-cell-contact and/or production of inhibitory cytokines like IL-10 or TGF-β. The current knowledge about the regulation of Treg suppressive function is limited. Toll-like receptors (TLR) are widely expressed in the innate immune system. They recognize conserved microbial ligands such as lipopolysaccharide, bacterial lipopeptides or viral and bacterial RNA and DNA. TLR play an essential role in innate immune responses and in the initiation of adaptive immune responses. However, certain TLR are also expressed in T lymphocytes, and the respective ligands can directly modulate T cell function. TLR2, TLR3, TLR5 and TLR9 act as costimulatory receptors to enhance proliferation and/or cytokine production of T-cell receptor-stimulated T lymphocytes. In addition, TLR2, TLR5 and TLR8 modulate the suppressive activity of naturally occurring CD4(+)CD25(high) Treg. The direct responsiveness of T lymphocytes to TLR ligands offers new perspectives for the immunotherapeutic manipulation of T cell responses. In this article we will discuss the regulation of Treg and other T cell subsets by TLR ligands.

Enteroantigen-presenting B cells efficiently stimulate CD4(+) T cells in vitro

BACKGROUND

Presentation of enterobacterial antigens by antigen-presenting cells and activation of enteroantigen-specific CD4(+) T cells are considered crucial steps in inflammatory bowel disease (IBD) pathology. The detrimental effects of such CD4(+) T cells have been thoroughly demonstrated in models of colitis. Also, we have previously established an in vitro assay where murine enteroantigen-specific colitogenic CD4(+) CD25(-) T cells are activated by splenocytes pulsed with an enterobacterial extract.

METHODS

CD4(+) CD25(-) T cells were stimulated in vitro with various kinds of enterobacterial extract-pulsed antigen-presenting cells. T-helper phenotypes were detected by flow cytometry.

RESULTS

We found that enteroantigen-pulsed splenic B cells possess a significantly higher and more sustained T cell stimulatory capacity than similarly pulsed splenic dendritic cells (DCs) measured by the level of enteroantigen-specific CD4(+) CD25(-) T cell proliferation. In support of this, we observed upregulation of classic maturation markers in B cells following incubation with enterobacterial antigens. Peritoneal and mesenteric lymph node-derived B cells were equally effective as enteroantigen-presenting stimulator cells. B cells greatly expanded the number of stimulated CD4(+) T cells, which acquired a T(H) 2 phenotype. Interestingly, regulatory T cells were primarily activated by enteroantigen-pulsed B cells but not by similarly pulsed DCs.

CONCLUSIONS

We conclude that B cells are superior stimulators of enteroantigen-specific CD4(+) T cells in vitro, favoring T(H) 2 polarization. Thus, enteroantigen-processing and -presentation by B cells instead of by DCs might have opposing consequences for IBD development.

FoxP3+ CD4+ T cells in systemic autoimmune diseases: the delicate balance between true regulatory T cells and effector Th-17 cells

Breakdown of tolerance is a hallmark of autoimmune diseases. Over the past 10 years, there has been increased interest in the role of FoxP3(+) regulatory T cells (T(Regs)) in maintaining peripheral tolerance. Dysfunction of these cells is considered to play a major role in the development of autoimmune diseases. Besides their suppressive function, a fraction of these cells has the capacity to differentiate into IL-17-producing cells (Th-17), a phenomenon associated with autoimmune inflammation. The revealed plasticity of T(Regs), therefore, has obvious implications when designing therapeutic strategies for restoring tolerance in autoimmune diseases using T(Regs). In this review, we discuss development, classification, molecular characterization and mechanisms of suppression by T(Regs). In addition, we describe recent data on their potential conversion into Th-17 cells in human systemic autoimmune diseases. We also outline a new strategy for T(Reg)-based therapy via isolation, expansion and re-infusion of highly pure FoxP3(+) T(Regs) free of contaminating effector T cells.

Platelet-rich plasma may prevent titanium-mesh exposure in alveolar ridge augmentation with anorganic bovine bone

OBJECTIVE

Bone augmentation with the titanium-mesh (Ti-mesh) technique is susceptible to a large rate of complications such as morbidity of bone graft donor site, and mesh exposure to the oral cavity. The purpose of this study was to evaluate the effectiveness of anorganic bovine bone (ABB) in alveolar bone augmentation with the Ti-mesh technique. In addition, we investigated the effect of platelet-rich plasma (PRP) in preventing mesh exposure by using it to cover the Ti-mesh.

PATIENTS AND METHODS

Patients included in the clinical trial were randomly allocated by a blinded assistant into two groups. The 30 patients recruited for this study underwent 43 alveolar bone augmentation with the Ti-mesh technique using ABB as graft material in all of them. In 15 patients, the Ti-meshes were covered with PRP (PRP group) whereas in the other 15 the Ti-meshes were not (control group). After 6 months, patients were called for clinical, radiographic, and histological evaluation, and implant placement surgery. A total of 97 implants were placed in the augmented bone and their evolution was followed up for a period of 24 months.

RESULTS

Significant differences were found between the two study groups in terms of complications and bone formation. In the control group, 28.5% of the cases suffered from mesh exposure, while in the PRP group, no exposures were registered. Radiographic analysis revealed that bone augmentation was higher in the PRP group than in the control group. Overall, 97.3% of implants placed in the control group and 100% of those placed in the PRP group were successful during the monitoring period. We suggest that the positive effect of PRP on the Ti-mesh technique is due to its capacity to improve soft tissue healing, thereby protecting the mesh and graft material secured beneath the gingival tissues.

CONCLUSIONS

Alveolar bone augmentation using ABB alone in the Ti-mesh technique is sufficient for implant rehabilitation. Besides, covering the Ti-meshes with PRP was a determining factor in avoiding mesh exposure. Ti-mesh exposure provoked significant bone loss, but in most cases it did not affect the subsequent placement of implants.

The PD-1 pathway in tolerance and autoimmunity

Regulatory T cells (Tregs) and the PD-1: PD-ligand (PD-L) pathway are both critical to terminating immune responses. Elimination of either can result in the breakdown of tolerance and the development of autoimmunity. The PD-1: PD-L pathway can thwart self-reactive T cells and protect against autoimmunity in many ways. In this review, we highlight how PD-1 and its ligands defend against potentially pathogenic self-reactive effector T cells by simultaneously harnessing two mechanisms of peripheral tolerance: (i) the promotion of Treg development and function and (ii) the direct inhibition of potentially pathogenic self-reactive T cells that have escaped into the periphery. Treg cells induced by the PD-1 pathway may also assist in maintaining immune homeostasis, keeping the threshold for T-cell activation high enough to safeguard against autoimmunity. PD-L1 expression on non-hematopoietic cells as well as hematopoietic cells endows PD-L1 with the capacity to promote Treg development and enhance Treg function in lymphoid organs and tissues that are targets of autoimmune attack. At sites where transforming growth factor-beta is present (e.g. sites of immune privilege or inflammation), PD-L1 may promote the de novo generation of Tregs. When considering the consequences of uncontrolled immunity, it would be therapeutically advantageous to manipulate Treg development and sustain Treg function. Thus, this review also discusses how the PD-1 pathway regulates a number of autoimmune diseases and the therapeutic potential of PD-1: PD-L modulation.

The cytokine milieu in the interplay of pathogenic Th1/Th17 cells and regulatory T cells in autoimmune disease

The propagation and regulation of an immune response is driven by a network of effector and regulatory T (Treg) cells. The interplay of effector T and Treg cells determines the direction of the immune response towards inflammation or its resolution in an autoimmune disease setting. In autoimmune diseases, this interplay shifts the balance in favor of the development of autoreactive effector T cells, resulting in inflammatory pathology. The objective of an effective therapeutic approach for autoimmune disease is to restore this balance. In this review, we describe the characteristics and development of pathogenic T helper 1 (Th1) and Th17 cells and the beneficial Treg cells in autoimmune diseases and the crucial roles of the cytokine milieu in influencing the balance of these T-cell subsets. Given the importance of cytokines, we discuss current immunotherapeutic strategies using cytokine or cytokine receptor antibodies for the treatment of autoimmune diseases.