CD25+ T cells and regulation of allergen-induced responses

Analysis of altered miRNA profiling in the colon of a mouse model with β-lactoglobulin allergy

OBJECTIVES

The differences in the expression profiles of colonic miRNAs between β-lactoglobulin (β-Lg) allergic mice and normal mice were analyzed to investigate the important role of the miRNA regulation mechanism in the pathogenesis of cow's milk allergy.

METHODS

The present study performed Illumina sequencing to characterize the miRNA profile changes in mouse colon responding to β-Lg challenge. Target genes were predicted by TargetScan 50 and miRanda 3.3a algorithms and assessed by GO and KEGG analysis. The expression levels of selected miRNAs and cytokine production were verified by cell transfection and quantitative RT-PCR.

RESULTS

A total of 15 miRNAs were diversely expressed between the colon of the normal and β-Lg-sensitized mice (P < 0.05, fold change of >1.50 or <0.67), including six up-regulated miRNAs and nine down-regulated miRNAs, among which seven miRNAs were validated using qRT-PCR. GO enrichment and KEGG pathway analyses further revealed that biological process, protein binding, cytoplasm and the pathways of cancer were significantly enriched, which were closely connected to the allergic inflammation development. Additionally, six key functional interaction pairs in β-Lg allergy were identified in miRNA prediction algorithms and verified using qRT-PCR.

CONCLUSIONS

We can conclude that our results suggested that the miRNAs regulation network participated in the pathogenesis of cow's milk allergy.

Luteolin attenuates airway inflammation by inducing the transition of CD4+CD25- to CD4+CD25+ regulatory T cells

Regulatory T cells play an important role in autoimmunity and have been shown to exert anti-inflammatory effects in allergic asthma. Mouse model of airway inflammation was used to examine the suppressive activity of luteolin-induced CD4⁺CD25⁺ regulatory T cells (Tregs) in vivo. In this study, BALB/c mice were sensitized with ovalbumin antigen (OVA) by aerosol challenge. Then, various biological processes were examined, including airway eosinophilia; mucus hypersecretion; elevation of OVA-specific IgE, expression of Th2 cytokines and chemokine levels; expression of eotaxin 2 and CCR3; and airway hyper responsiveness (AHR). Luteolin significantly inhibited OVA-induced increase in immune cell and eosinophil counts as well as IL-4, IL-5, IL-13, and eotaxin levels in bronchoalveolar lavage fluid (BAL Fluid). Luteolin and cyclosporine A (CsA) which was a positive control also substantially reduced OVA-specific IgE levels, eotaxin 2 levels, and CCR3 expression in BAL Fluid. In contrast, luteolin significantly increased IL-10 and IFN-γ protein levels, as well as IL-10 and TGF-β1 mRNA expression in the lung. In vitro studies showed that the number of luteolin-induced CD4⁺CD25⁺ Treg (iTreg) cells was higher, with elevated levels of TGF-β1 and foxp3 mRNA expression in lungs tissue. Transfer of iTreg cells into OVA-sensitized mice reduced AHR, eosinophil recruitment, eotaxin, IgE, and Th2 cytokine expressions, and increased IFN-γ production in BAL Fluid after allergen challenge. Furthermore, adoptive transfer of iTreg cells prevented disease in a CD25-depleted mouse asthma model. Luteolin via induction of foxp3 and CD4⁺CD25⁺ Treg cells may represent a new strategy in the development of therapies for managing asthma.

The relative values of CD8+CD25+Foxp3brigh Treg cells correlate with selected lung function parameters in asthma

The study aimed to detect CD8(+)CD25(+)FoxP3(brigh) Tregs and investigate their possible association with selected lung function values. CD8(+)CD25(+)FoxP3(brigh) Tregs were detected by flow cytometry in the peripheral blood of 25 patients with severe asthma (SA), 25 patients with mild-to-moderate asthma (MA), and 25 age-matched healthy donors (NC). The percentages of CD8(+)CD25(+)FoxP3(brigh) Tregs of the patients with severe (3.4 ± 4.55), and mild-to-moderate asthma (7.5 ± 8.15), were markedly lower than those of controls (12.1 ± 13.2). The mean forced expiratory volume in 1 s (FEV1) % predicted value in severe asthma subpopulation was significantly lower (67.05 ± 15.98%) when compared with that of mild-to-moderate asthma subgroup (87.71 ± 16.12%). Interestingly, the percentages of CD8(+)CD25(+)FoxP3(brigh) Tregs correlate with mean peak expiratory flow (PEF)% predicted values in severe (r = 0.7, P <0.01) and mild-to-moderate (r = 0.73, P <0.01) asthma. In contrast, this parameter was positively correlated with FEV1% predicted values in the severe asthmatics only (r = 0.71, P <0.01). In summary, this study establishes a link between the percentage of CD8(+)CD25(+)FoxP3(brigh) Tregs and selected lung function parameters, suggesting that this parameter has potential as a marker for inflammation and airflow obstruction.

The biology of pulmonary aspergillus infections

Pulmonary aspergillus infections are mainly caused by Aspergillus fumigatus and can be classified based on clinical syndromes into saphrophytic infections, allergic disease and invasive disease. Invasive pulmonary aspergillosis, occurring in immunocompromised patients, reflects the most serious disease with a high case-fatality rate. Patients with cystic fibrosis and severe asthma might develop allergic bronchopulmonary aspergillosis, while saphrophytic infections are observed in patients with lung cavities mainly due to tuberculosis. Histopathologically, a differentiation can be made into angio-invasive and airway-invasive disease. If the host response is too weak or too strong, Aspergillus species are able to cause disease characterized either by damage from the fungus itself or through an exaggerated inflammatory response of the host, in both situations leading to overt disease associated with specific clinical signs and symptoms. The unraveling of the specific host - Aspergillus interaction has not been performed to a great extent and needs attention to improve the management of those clinical syndromes.

The potential mechanistic link between allergy and obesity development and infant formula feeding

This article provides a new view of the cellular mechanisms that have been proposed to explain the links between infant formula feeding and the development of atopy and obesity. Epidemiological evidence points to an allergy- and obesity-preventive effect of breastfeeding. Both allergy and obesity development have been traced back to accelerated growth early in life. The nutrient-sensitive kinase mTORC1 is the master regulator of cell growth, which is predominantly activated by amino acids. In contrast to breastfeeding, artificial infant formula feeding bears the risk of uncontrolled excessive protein intake overactivating the infant's mTORC1 signalling pathways. Overactivated mTORC1 enhances S6K1-mediated adipocyte differentiation, but negatively regulates growth and differentiation of FoxP3(+) regulatory T-cells (Tregs), which are deficient in atopic individuals. Thus, the "early protein hypothesis" not only explains increased mTORC1-mediated infant growth but also the development of mTORC1-driven diseases such as allergy and obesity due to a postnatal deviation from the appropriate axis of mTORC1-driven metabolic and immunologic programming. Remarkably, intake of fresh unpasteurized cow's milk exhibits an allergy-preventive effect in farm children associated with increased FoxP3(+) Treg numbers. In contrast to unprocessed cow's milk, formula lacks bioactive immune-regulatory microRNAs, such as microRNA-155, which plays a major role in FoxP3 expression. Uncontrolled excessive protein supply by formula feeding associated with the absence of bioactive microRNAs and bifidobacteria in formula apparently in a synergistic way result in insufficient Treg maturation. Treg deficiency allows Th2-cell differentiation promoting the development of allergic diseases. Formula-induced mTORC1 overactivation is thus the critical mechanism that explains accelerated postnatal growth, allergy and obesity development on one aberrant pathway.

Parity, age at first birth, and risk of death from asthma: evidence from a cohort in taiwan

This study was undertaken to examine whether there is an association between age at first birth and parity and risk of asthma death. The study cohort consisted of 1,292,462 women in Taiwan who had a first live birth between 1 January 1978 and 31 December 1987. We tracked each woman from the date of their first childbirth to 31 December 2009, and their vital status was ascertained by linking records with the computerized mortality database. Cox proportional hazard regression models were used to estimate hazard ratios of death from asthma associated with parity and age at first birth. A trend of increasing risk of asthma death was seen with increasing age at first birth. The adjusted hazard ratio was 0.75 (95% confidence interval (CI) = 0.53–1.08) among women with two live births and 0.53 (95% CI = 0.36–0.78) among those with three or more births, compared with women who had one live birth. There was a significant decreasing trend in adjusted hazard ratios of asthma death with increasing parity. This study is the first to provide evidences to support an association between reproductive factors (parity and early age at first birth) and the risk of asthma death.

Subsets of regulatory T cells and their roles in allergy

In recent years, it is recognized that acquired immunity is controlled by regulatory T cell (Treg). Since fundamental pathophysiological changes of allergy are mainly caused by hyperresponsiveness of immune system to allergens that acquires after birth, Tregs likely play key roles in the pathogenesis of allergy, particularly during the sensitization phase. However, accumulated information indicate that there are several distinctive subtypes of Tregs in man, and each of them seems to play different role in controlling immune system, which complicates the involvement of Tregs in allergy. The aim of the present study is to attempt to classify subtypes of Tregs and summarize their roles in allergy. Tregs should include natural Tregs (nTreg) including inducible costimulator (ICOS)(+) Tregs, inducible/adaptive Tregs (iTreg), interleukin (IL)-10-producing type 1 Tregs (Tr1 cells), CD8(+) Tregs and IL-17-producing Tregs. These cells share some common features including expression of Foxp3 (except for Tr1 cells), and secretion of inhibitory cytokine IL-10 and/or TGF-β. Furthermore, it is noticeable that Tregs likely contribute to allergic disorders such as dermatitis and airway inflammation, and play a crucial role in the treatment of allergy through their actions on suppression of effector T cells and inhibition of activation of mast cells and basophils. Modulation of functions of Tregs may provide a novel strategy to prevent and treat allergic diseases.

Milk: an exosomal microRNA transmitter promoting thymic regulatory T cell maturation preventing the development of atopy?

Epidemiological evidence confirmed that raw cow's milk consumption in the first year of life protects against the development of atopic diseases and increases the number of regulatory T-cells (Tregs). However, milk's atopy-protective mode of action remains elusive.This review supported by translational research proposes that milk-derived microRNAs (miRs) may represent the missing candidates that promote long-term lineage commitment of Tregs downregulating IL-4/Th2-mediated atopic sensitization and effector immune responses. Milk transfers exosomal miRs including the ancient miR-155, which is important for the development of the immune system and controls pivotal target genes involved in the regulation of FoxP3 expression, IL-4 signaling, immunoglobulin class switching to IgE and FcϵRI expression. Boiling of milk abolishes milk's exosomal miR-mediated bioactivity. Infant formula in comparison to human breast- or cow's milk is deficient in bioactive exosomal miRs that may impair FoxP3 expression. The boost of milk-mediated miR may induce pivotal immunoregulatory and epigenetic modifications required for long-term thymic Treg lineage commitment explaining the atopy-protective effect of raw cow's milk consumption.The presented concept offers a new option for the prevention of atopic diseases by the addition of physiological amounts of miR-155-enriched exosomes to infant formula for mothers incapable of breastfeeding.

Genotype-dependent effects of TGF-β1 on mast cell function: targeting the Stat5 pathway

We previously demonstrated that TGF-β1 suppresses IgE-mediated signaling in human and mouse mast cells in vitro, an effect that correlated with decreased expression of the high-affinity IgE receptor, FcεRI. The in vivo effects of TGF-β1 and the means by which it suppresses mast cells have been less clear. This study shows that TGF-β1 suppresses FcεRI and c-Kit expression in vivo. By examining changes in cytokine production concurrent with FcεRI expression, we found that TGF-β1 suppresses TNF production independent of FcεRI levels. Rather, IgE-mediated signaling was altered. TGF-β1 significantly reduced expression of Fyn and Stat5, proteins critical for cytokine induction. These changes may partly explain the effects of TGF-β1, because Stat5B overexpression blocked TGF-mediated suppression of IgE-induced cytokine production. We also found that Stat5B is required for mast cell migration toward stem cell factor, and that TGF-β1 reduced this migration. We found evidence that genetic background may alter TGF responses. TGF-β1 greatly reduced mast cell numbers in Th1-prone C57BL/6, but not Th2-prone 129/Sv mice. Furthermore, TGF-β1 did not suppress IgE-induced cytokine release and did increase c-Kit-mediated migration in 129/Sv mast cells. These data correlated with high basal Fyn and Stat5 expression in 129/Sv cells, which was not reduced by TGF-β1 treatment. Finally, primary human mast cell populations also showed variable sensitivity to TGF-β1-mediated changes in Stat5 and IgE-mediated IL-6 secretion. We propose that TGF-β1 regulates mast cell homeostasis, and that this feedback suppression may be dependent on genetic context, predisposing some individuals to atopic disease.

Granzyme B is not required for regulatory T cell-mediated suppression of graft-versus-host disease

Regulatory T (T(reg)) cells can suppress a wide variety of immune responses, including antitumor and alloimmune responses. The mechanisms by which T(reg) cells mediate their suppressive effects depend on the context of their activation. We previously reported that granzyme B is important for T(reg) cell-mediated suppression of antitumor immune responses. We therefore hypothesized that granzyme B may likewise be important for suppression of graft-versus-host disease (GVHD). We found that allogeneic mismatch induces the expression of granzyme B in mixed lymphocyte reactions and in a model of graft-versus-host disease (GVHD). However, wild-type and granzyme B-deficient T(reg) cells were equally able to suppress effector T (T(eff)) cell proliferation driven by multiple stimuli, including allogeneicantigen-presenting cells. Surprisingly, adoptive transfer of granzyme B-deficient T(reg) cells prevented GVHD lethality, suppressed serum cytokine production in vivo, and prevented target organ damage. These data contrast strikingly with our previous study, which demonstrated that granzyme B plays a nonredundant role in T(reg) cell-mediated suppression of antitumor responses. Taken together, these findings suggest that targeting specific T(reg) cell-suppressive mechanisms, such as granzyme B, may be therapeutically beneficial for segregating GVHD and graft-versus-tumor immune responses.

Bromelain treatment reduces CD25 expression on activated CD4+ T cells in vitro

Bromelain (Br), an extract from pineapple stem with cysteine protease activity, exerts anti-inflammatory effects in a number of inflammatory models. We have previously shown that Br treatment decreased activated CD4(+) T cells and has a therapeutic role in an ovalbumin-induced murine model of allergic airway disease. The current study was designed to determine the effect of Br on CD4(+) T cell activation, specifically the expression of CD25 in vitro. CD25 is up regulated upon T cell activation, found as a soluble fraction (sCD25) and is a therapeutic target in inflammation, autoimmunity and allergy. Br treatment of anti-CD3 stimulated CD4(+) T cells reduced CD25 expression in a dose and time dependent manner. This reduction of CD25 was dependent on the proteolytic action of Br as the addition of E64 (a cysteine protease inhibitor) abrogated this response. The concentration of sCD25 was increased in supernatants of Br treated activated CD4(+) T cells as compared to control cells, suggesting that Br proteolytically cleaved cell-surface CD25. This novel mechanism of action identifies how Br may exert its therapeutic benefits in inflammatory conditions.

Pathogenesis of allergic bronchopulmonary aspergillosis in cystic fibrosis: current understanding and future directions

Allergic bronchopulmonary aspergillosis (ABPA) is an allergic disease characterized clinically by wheezing, pulmonary infiltrates, bronchiectasis, and fibrosis that affects patients with asthma and cystic fibrosis (CF). Although this disease has been characterized by a Th2 immune response to Aspergillus, the disease has some features such as central bronchiectasis which is not seen in other Th2 driven lung diseases such as atopic asthma. Here we will review the current pathophysiology of ABPA in CF and highlight new molecules that may affect immune responses against Aspergillus and ABPA disease pathogenesis.

GATA3-driven Th2 responses inhibit TGF-beta1-induced FOXP3 expression and the formation of regulatory T cells

Transcription factors act in concert to induce lineage commitment towards Th1, Th2, or T regulatory (T_reg) cells, and their counter-regulatory mechanisms were shown to be critical for polarization between Th1 and Th2 phenotypes. FOXP3 is an essential transcription factor for natural, thymus-derived (nT_reg) and inducible T_reg (iT_reg) commitment; however, the mechanisms regulating its expression are as yet unknown. We describe a mechanism controlling iT_reg polarization, which is overruled by the Th2 differentiation pathway. We demonstrated that interleukin 4 (IL-4) present at the time of T cell priming inhibits FOXP3. This inhibitory mechanism was also confirmed in Th2 cells and in T cells of transgenic mice overexpressing GATA-3 in T cells, which are shown to be deficient in transforming growth factor (TGF)-β–mediated FOXP3 induction. This inhibition is mediated by direct binding of GATA3 to the FOXP3 promoter, which represses its transactivation process. Therefore, this study provides a new understanding of tolerance development, controlled by a type 2 immune response. IL-4 treatment in mice reduces iT_reg cell frequency, highlighting that therapeutic approaches that target IL-4 or GATA3 might provide new preventive strategies facilitating tolerance induction particularly in Th2-mediated diseases, such as allergy.

Specific immune responses against foreign or autologous antigens are driven by specialized epitope-specific T cells, whose numbers expand upon recognition of antigen found on professional antigen-presenting cells. The subsequent maturation process involves the differentiation of certain T cell phenotypes such as pro-inflammatory cells (Th1, Th2, Th17) or regulatory T (T_reg) cells, which serve to keep the immune response in check. The current study focuses on the role of two key transcription factors—FOXP3 and GATA3—in controlling the commitment of these cells. We demonstrate that the Th2 cytokine IL-4 inhibits the induction of FOXP3 and thus inhibits the generation of inducible T_reg cells. We show that IL-4–induced GATA3 mediates FOXP3 inhibition by directly binding to a GATA element in the FOXP3 promoter. We hypothesize that therapeutic agents aimed at neutralizing IL-4 could be a novel strategy to facilitate inducible T_reg cell generation and thus promotion of tolerance in allergies and other Th2-dominated diseases.

It is shown that Th2 responses prevent the generation of inducible T_regs. This is mediated by IL-4 induction of GATA3, which binds directly to and represses the FOXP3 promoter. This mechanism is likely to be relevant in the induction of immunotolerance, particularly in allergic diseases.

Mechanisms of action of regulatory T cells specific for paternal antigens during pregnancy

OBJECTIVE

To investigate whether pregnancy-induced regulatory T cells are generated specifically for paternal antigens or expanded by hormonal changes and to study regulatory T cell-related mechanisms during pregnancy.

METHODS

We used murine models of normal, abortion-prone, and pseudopregnancy to characterize regulatory T cells and hormones by methods such as flow cytometry, molecular biology techniques, and chemiluminescence. Antigen specificity was studied in experiments in which animals were vaccinated with paternal antigens or adoptively transferred with regulatory T cells. To analyze regulatory T cell-mediated mechanisms, we used neutralizing antibodies against IL-10 or TGF-beta.

RESULTS

Regulatory T cells are activated by male antigens, and minor antigens are protected by linked immunosuppression. Our data exclude the possibility that regulatory T cell expansion during pregnancy is exclusively driven by hormonal changes. An increase in systemic regulatory T cell levels in pseudopregnant females after mating with vasectomized males but not after pseudopregnancy induced mechanically confirms generation of regulatory T cells specific for paternal antigens. As for the mechanisms, neutralizing IL-10 abrogates the protective effect of regulatory T cells, whereas blockage of TGF-beta does not provide the same effect.

CONCLUSION

Our data confirm that regulatory T cells act in an antigen-specific manner during pregnancy and strongly suggest that IL-10 is involved in regulatory T cell-mediated protection of the fetus. These data contribute to the knowledge of the basic mechanisms regulating immune tolerance during pregnancy, a major biologic question with important medical implications.

LEVEL OF EVIDENCE

II.

Cloning of feline FOXP3 and detection of expression in CD4+CD25+ regulatory T cells

Regulatory T cells (Treg) are increased and directly infected by feline immunodeficiency virus (FIV) and likely play a role in other feline autoimmune, neoplastic, and infectious diseases. Phenotypically, Treg are best characterized by surface expression of CD4 and CD25 and intranuclear expression of the forkhead transcription factor Foxp3. Our objective was to clone and sequence feline FOXP3 for the purpose of developing assays to enhance studies of feline Treg. We determined the feline FOXP3 is 1293 nucleotides in length and codes for a protein that shares high homology to other species. A splice variant devoid of exon 2 was also identified. A real-time PCR assay was developed and used to show Foxp3 mRNA expression occurs primarily in CD4+CD25+ T cells. Two cross-reacting antibodies were identified by immunocytochemical staining of HEK293 cells transfected with feline FOXP3. The antibody labeling confirmed the nuclear localization of the protein. A flow cytometric assay was also validated and used to correlate the phenotypic and functional characteristics of feline Treg induced by treatment of lymph node lymphocytes with flagellin or LPS in combination with mitogen or IL2. Together, these studies provide useful tools to further investigate Foxp3 and Tregs in cats.

Immunoreactivity profile of peripheral blood mononuclear cells from patients with ragweed-induced allergic rhinitis

BACKGROUND

Seasonal rhinitis is manifested by a series of nasal symptoms in response to exposure to seasonal allergens including ragweed pollen. Understanding its immunological mechanisms may help to better manage the disease.

OBJECTIVE

We sought to determine comprehensively ragweed-induced cytokine and chemokine production by peripheral blood mononuclear cells from normal individuals and patients with seasonal rhinitis sensitized to ragweed pollen, and to assess its regulation by exogenous IL-10.

METHODS

Cells were cultured in the presence or absence of a purified ragweed pollen extract with or without exogenous IL-10. Cytokines and chemokines were measured in the supernatant. Gene expression was evaluated using real-time quantitative reverse transcription PCR.

RESULTS

Ragweed stimulation significantly increased the production of the Th2-associated cytokines IL-5, IL-9 and IL-13, the chemokines CCL17 and CCL22 and the regulatory cytokine IL-10 in allergic patients, whereas transforming growth factor-beta (TGF-beta) production was increased only in normal individuals. No difference was detected between groups in the production of the Th1 cytokine IFN-gamma or the Th1-affiliated chemokines CXCL10 and CXCL11. Exogenous IL-10 significantly suppressed spontaneous and induced production of both Th1- and Th2-associated cytokines and chemokines.

CONCLUSION

Our work demonstrated that locally manifested allergic rhinitis is underlined by a systemic Th2 immune response specific to allergens. The molecular pathogenesis of allergic rhinitis may be linked to a compromised allergen-specific immune regulation, e.g., reduced spontaneous and allergen-induced TGF-beta production in patients compared with healthy controls. Our data also show that IL-10 inhibits both the effector and directional mechanisms of allergen-specific immune response, further supporting its potential therapeutic benefit in preventing and treating allergic diseases.

Are there reasons why adult asthma is more common in females?

Many epidemiological studies suggest that women are at increased risk of developing adult-onset asthma and also suffer from more severe disease than men. These gender differences appear to be the product of biological sex differences as well as sociocultural and environmental differences. The biological sex differences include genetic, pulmonary, and immunological factors. There is compelling evidence that sex hormones are major determinants of at least these biological sex differences. This paper explores the current literature regarding effects of sex hormones on immune function, resident lung cells, and regulation of local processes in the lung to shed light on underlying mechanisms of gender differences in asthma. More research is needed to understand these mechanisms in order to improve treatment of women with asthma.

CD4+CD25+ T cells protect against experimentally induced asthma and alter pulmonary dendritic cell phenotype and function

The role of natural CD4+CD25+ regulatory T (T reg) cells in the control of allergic asthma remains poorly understood. We explore the impact of T reg cell depletion on the allergic response in mice susceptible (A/J) or comparatively resistant (C3H) to the development of allergen-induced airway hyperresponsiveness (AHR). In C3H mice, anti-CD25-mediated T reg cell depletion before house dust mite treatment increased several features of the allergic diathesis (AHR, eosinophilia, and IgE), which was concomitant with elevated T helper type 2 (Th2) cytokine production. In similarly T reg cell-depleted A/J mice, we observed a moderate increase in airway eosinophilia but no effects on AHR, IgE levels, or Th2 cytokine synthesis. As our experiments suggested that T reg cell depletion in C3H mice before sensitization was sufficient to enhance the allergic phenotype, we characterized dendritic cells (DCs) in T reg cell-depleted C3H mice. T reg cell-depleted mice had increased numbers of pulmonary myeloid DCs with elevated expression of major histocompatibility complex class II, CD80, and CD86. Moreover, DCs from T reg cell-depleted mice demonstrated an increased capacity to stimulate T cell proliferation and Th2 cytokine production, which was concomitant with reduced IL-12 expression. These data suggest that resistance to allergen-driven AHR is mediated in part by CD4+CD25+ T reg cell suppression of DC activation and that the absence of this regulatory pathway contributes to susceptibility.