Exopolysaccharide from Lacticaseibacillus rhamnosus induces IgA production in airways and alleviates allergic airway inflammation in mouse model

The currently observed high prevalence of allergic diseases has been associated with changes in microbial exposure in industrialized countries. Defined bacterial components represent a new strategy for modulating the allergic immune response. We show that intranasal administration of exopolysaccharide (EPS) isolated from Lacticaseibacillus (L.) rhamnosus LOCK900 induces TGF-β1, IgA, and regulatory FoxP3⁺ T-cells in the lungs of naïve mice. Using the ovalbumin mouse model, we demonstrate that intranasal administration of EPS downregulates the development of allergic airway inflammation and the Th2 cytokine response in sensitized individuals. At the same time, EPS treatment of sensitized mice, similar to EPS-induced responses in naïve mice, significantly increased the level of total, OVA-specific, and also bacteria-specific IgA in bronchoalveolar lavage and the number of IgA-producing B-cells in the lung tissue of these mice. Thus, EPS derived from L. rhamnosus LOCK900 can be considered a safe candidate for preventing the development of allergic symptoms in the lungs of sensitized individuals upon exposure to an allergen.     

Effects of furosemide on allergic asthmatic responses in mice

Background The syndrome of allergic asthma features reversible bronchoconstriction, airway inflammation and hyperresponsiveness as well as airway remodelling, including goblet cell hyperplasia. Managing severe asthma is still a clinical challenge. Numerous studies report that furosemide, an inhibitor of Na⁺–K⁺–Cl^? cotransporter (NKCC) reduces airway hyperresponsiveness (AHR) in asthmatic patients. However, the mechanism by which furosemide exerts anti‐asthmatic action remains unclear. Objective This study sought to investigate the cellular profile of NKCC1 expression in the lung and examine the effects of furosemide on several outcome measurements in a mouse model of allergic asthma. Methods Mice were sensitized and challenged with ovalbumin (OVA). Before challenge, the OVA‐sensitized mice were treated with furosemide (4.0 mg/kg/day, via daily intraperitoneal injection for 5 days). Outcome measurements in naïve, OVA‐exposure, furosemide‐treated naïve and furosemide‐treated OVA‐exposed mice included the slope of the relationship between inhaled methacholine (MCh) concentration and respiratory system resistance (Slope·R_RS), bronchoalveolar lavage (BAL) cell counts and immunohistochemical and immunoblotting assays of lung tissues. Results NKCC1 immunoreactivity was observed in airway epithelial cells (AECs) and alveolar type II (ATII) cells of the control mice. OVA exposure enhanced the expression of NKCC1 in AECs and ATII cells, and increased the infiltration of NKCC1‐expressing T lymphocytes in the lung. NKCC1 immunoreactivity was not detected in the airway smooth muscle (ASM) cells. Furosemide treatment reduced the Slope·R_RS in both naïve and OVA‐exposed mice by about 50%. Furosemide treatment also increased T lymphocyte infiltration to the lung in OVA‐exposed mice by approximately 53%, but had no effect on pulmonary goblet cell hyperplasia. Conclusions and Clinical Relevance Furosemide decreases basal airway responsiveness, thereby reducing the extent of allergen‐induced AHR. However, the same treatment also increases T lymphocytes infiltration in the course of allergic asthma. Further studies are necessary to address the usefulness of furosemide in the clinical treatment of asthma. Cite this as: S. Wang, Y.‐Y. Xiang, R. Ellis, J. Wattie, M. Feng, M. D. Inman and W.‐Y. Lu, Clinical & Experimental Allergy, 2011 (41) 1456–1467.     

Adoptive transfer of dendritic cells from allergic mice induces specific immunoglobulin E antibody in naïve recipients in absence of antigen challenge without altering the T helper 1/T helper 2 balance

Dendritic cells (DCs) are important in the regulation of immune responses and it has been proposed that these cells play an important role in asthma; however, their role in food allergy is still largely unknown. Our aim was to study specific immunoglobulin E (IgE) and immunoglobulin G (IgG) responses in naïve recipients following adoptive transfer of myeloid DCs from allergic and control mice. The phenotypic features and lymphokine production of DCs were also investigated. CD11c ^{+ /hi} B220^? DCs isolated from spleen and Peyer's patches (PP) of cow's milk (CM) allergic and control mice were transferred intravenously (i.v.) into naïve syngeneic recipients, and IgE‐ and IgG‐specific responses were evaluated. Experiments were also carried out to determine the levels of interferon‐γ (IFN‐γ) and interleukin (IL)‐4 produced by splenocytes from naïve recipients following the adoptive transfer, and CD40 ligand (CD40L)‐mediated IL‐10 production by DCs from allergic and control mice. DCs isolated from spleen and PP of allergic mice, but not control groups, induced CM‐specific IgG and IgE antibody production in naïve recipients in the absence of previous immunization, but did not modify the T helper 1 (Th1) and T helper 2 (Th2) balance. Furthermore, although no difference was observed in the expression of canonical DC surface markers, PP DCs from allergic mice produced less IL‐10 than DCs from controls. We interpret these data as showing that DCs play a pivotal role in allergen‐specific IgE responses and that a Th2‐skewed response may not be involved in the early phase of allergic responses. The identification of the mechanisms underlying these events may help to design novel strategies of therapeutic intervention in food allergy.     

Genetic selection for resistance or susceptibility to oral tolerance imparts correlation to both Immunoglobulin E level and mast cell number phenotypes with a profound impact on the atopic potential of the individual

Background Immunological oral tolerance is being studied with great interest due to its therapeutic potential in allergy and autoimmunity processes, although the cellular and molecular mechanisms linking these different phenomena remain elusive. In the present study, two mouse lines with extreme phenotypes for susceptibility [TS Line] or resistance [TR Line] to oral tolerance and their [TS × TR]F₂ segregants were used in order to evaluate the impact of these traits on the atopic potential of the individuals. Objective Demonstrate whether the tr and ts genes, cumulated during 18 generations of bidirectional genetic selection, influence expression of two important immunobiological traits (IgE and mast cell) critical to allergic response. Methods Mice with extreme phenotypes for oral tolerance to ovalbumin (OVA), produced by assortative mating (TS and TR Line), and their (TS × TR)F₂ segregating were used. Serum IgE levels assayed by ELISA, and mastocytes counted with toluidine blue staining were evaluated in naïve mice. Anaphylaxis was induced by intravenous injection of OVA, intestinal inflammation by oral administration of OVA 7 days after immunization, and pulmonary inflammation by intranasal and nebulization OVA challenges. Specific IgE was dosed by passive cutaneous anaphylaxis. Results The naïve TS mice have a 20‐fold lower serum IgE level and two‐ to threefold diminished mast cell numbers in mucosal sites, when compared with TR‐mice, which were highly susceptible to allergic inflammation and anaphylactic shock. The associations of oral tolerance, serum IgE levels and mast cell numbers in naïve animals were confirmed analysing the simultaneous presence of these traits in individuals of a [TS × TR]F₂‐segregating population. Conclusion The results suggest that the complex of genes controlling TS and TR phenotypes play a main role in the regulation of the atopic potential of the individual. The studies of these traits in interline F₂ segregants demonstrated a co‐segregation of TS and TR phenotypes with IgE responsiveness and mast cell numbers. Thus, the opposite capacity of the genetically modified mice may be involved in co‐adaptative mechanisms reflecting a dynamic relation between gene frequencies in a natural population. These correlations give circumstantial evidence to support clinical applications of oral tolerance in allergic and autoimmune diseases.     

Maternal tolerance achieved during pregnancy is transferred to the offspring via breast milk and persistently protects the offspring from allergic asthma

Background Maternal, more than paternal, asthma is a risk factor for the development of asthma in children. Recently, epidemiologic studies have shown that environmental exposures during pregnancy might influence the development of childhood asthma and allergies. Objective The aim of the present study was to investigate whether the induction of tolerance against a specific antigen during pregnancy prevents in the offspring the development of allergic asthma in response to this antigen. Methods Balb/c mice were orally tolerized with ovalbumin (OVA) during pregnancy. The offspring of tolerized and naïve mothers were immunized with OVA at 6 weeks and 4 months of age and analysed in our murine asthma model. Results While the offspring of naïve mice developed increased AHR, eosinophilic airway inflammation, T‐helper type 2 cytokine production and high serum IgE levels in response to OVA sensitization, the offspring of tolerized mice were almost completely protected from asthma, even when immunized as late as 4 months after birth. Breastfeeding was crucial for protection because tolerance was only observed when the offspring were nursed by their own mothers and not when nursed by naïve wet‐nurses. Allergen‐specific IgG₁ antibodies were exclusively increased in the breast milk of tolerant mothers and serum of protected pups, indirectly supporting its important role in tolerance transfer from the mother to the offspring. Sensitization of the F1 generation from OVA‐tolerized mothers with a heterologous allergen enhanced the immune response to this antigen. Conclusion Our results demonstrate that mucosal allergen contact during pregnancy modifies the asthma and allergy risk of the offspring mediated via breast milk. This observation may suggest that the time window for primary prevention strategies starts even before early childhood during pregnancy.     

Role of miR-146a in Enforcing Effect of Specific Immunotherapy on Allergic Rhinitis

Allergic rhinitis (AR) is one of the common disorders in airway allergic inflammation. The pathogenesis of AR is unclear. It is accepted that immune deregulation is associated with the pathogenesis of AR. Recent reports suggest that a large number of micro RNAs (miR) can regulate immune functions. This study aims to investigate the role of miR-146a in an enforcing immunotherapy of AR. In this study, a mouse AR model was created. The levels of miR-146a in the mouse nasal mucosa were assessed by real time RT-PCR. A specific immunotherapy was performed in AR mice. The results showed that the AR mice had an AR-like inflammation in the nasal mucosa. Compared with naïve mice, markedly lower levels of miR-146a were detected in AR mice. The co-administration with miR-146a significantly enforced the effect of ovalbumin (OVA)-specific immunotherapy on inhibition of AR inflammation in the nasal mucosa. Further analysis showed that miR-146a induced transforming growth factor-β in dendritic cells; the latter induced naïve CD4⁺ T cells to differentiate into regulatory T cells. In conclusion, miR-146a can enforce OVA-specific immunotherapy via inducing antigen-specific regulatory T cells. miR-146a may have therapeutic potential to be used in the immunotherapy of allergic diseases.     

A low dose of Mycoplasma pneumoniae infection enhances an established allergic inflammation in mice: the role of the prostaglandin E2 pathway

Background Over 40% of chronic stable asthma patients have evidence of respiratory Mycoplasma pneumoniae (Mp) infection as detected by PCR, but not by serology and culture, suggesting that a low‐level Mp is involved in chronic asthma. However, the role of such a low‐level Mp infection in the regulation of allergic inflammation remains unknown. Objective To determine the impact of a low‐level Mp infection in mice with established airway allergic inflammation on allergic responses such as eosinophilia and chemokine eotaxin‐2, and the underlying mechanisms [i.e. the prostaglandin E₂ (PGE₂) pathway] since PGE₂ inhalation before an allergen challenge suppressed the eosinophil infiltration in human airways. Methods BALB/c mouse models of ovalbumin (OVA)‐induced allergic asthma with an ensuing low‐ or high‐dose Mp were used to assess IL‐4 expression, bronchoalveolar lavage (BAL) eosinophil, eotaxin‐2 and PGE₂ levels, and lung mRNA levels of microsomal prostaglandin E synthase‐1 (mPGES‐1). Primary alveolar macrophages (pAMs) from naïve BALB/c mice were cultured to determine whether Mp‐induced PGE₂ or exogenous PGE₂ down‐regulates IL‐4/IL‐13‐induced eotaxin‐2. Results Low‐dose Mp in allergic mice significantly enhanced IL‐4 and eotaxin‐2, and moderately promoted lung eosinophilia, whereas high‐dose Mp significantly reduced lung eosinophilia and tended to decrease IL‐4 and eotaxin‐2. Moreover, in both OVA‐naïve and allergic mice, lung mPGES‐1 mRNA and BAL PGE₂ levels were elevated in mice infected with high‐dose, but not low‐dose Mp. In pAMs, IL‐4/IL‐13 significantly increased eotaxin‐2, which was reduced by Mp infection accompanied by dose‐dependent PGE₂ induction. Exogenous PGE₂ inhibited IL‐4/IL‐13‐induced eotaxin‐2 in a dose‐dependent manner. Conclusions This study highlights a novel concept on how different bacterial loads in the lung modify the established allergic airway inflammation and thus interact with an allergen to further induce Th2 responses. That is, unlike high‐level Mp, low‐level Mp fails to effectively induce PGE₂ to down‐regulate allergic responses (e.g. eotaxin‐2), thus maintaining or even worsening allergic inflammation in asthmatic airways.     

Allergen-induced bronchial inflammation is associated with decreased levels of surfactant proteins A and D in a murine model of asthma

Background Increasing evidence suggests that pulmonary surfactant protein A (SP‐A) and D (SP‐D) participate in the lung defence against pathogens. However, the role of surfactant proteins in the pathogenesis of allergen‐induced airway inflammation has not been elucidated. In this study we examined the levels and distributions of SP‐A and SP‐D in a dust mite (Dermatophagoides pteronyssinus, Der p) allergen‐induced murine model of asthma. Methods The concentration of SP‐A and SP‐D in the bronchoalveolar lavage fluid (BALF) and the distribution of surfactant proteins in the lung were assayed by ELISA and immunohistochemistry methods, respectively. The effect of surfactant proteins on allergen‐induced pulmonary lymphocyte proliferation was also studied. Results We demonstrated that there were marked reductions of SP‐A and SP‐D levels in the BALF of Der p‐sensitized BALB/c mice at 48–72 h after allergen challenge (AC). Both purified SP‐A and SP‐D were able to suppress, in a dose dependent manner, Der p‐stimulated intrapulmonary lymphocyte proliferation of naïve mice with saline or allergen challenge, or of Der p‐sensitized mice with saline challenge. On the contrary, this suppressive effect was mild (< 9%) on lymphocytes from sensitized mice after AC. Conclusion These results indicated the involvement of pulmonary surfactant proteins in the allergic bronchial inflammation of sensitized mice.     

Disruption of the Notch pathway aggravates airway inflammation by inhibiting regulatory T cell differentiation via regulation of plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) regulate immunity and promote tolerance in asthma. Notch signalling is a highly conserved pathway that regulates the immune response; however, its role in pDC-mediated asthmatic airway inflammation is unclear. This study clarified the effects of Notch signalling on pDC-mediated airway inflammation using murine models of ovalbumin-sensitized allergic asthma. RBP-J-deficient pDCs (RBP-J^−/− pDCs) were co-cultured with naïve CD4⁺ T cells and supernatants and T cell subtypes were analysed. RBP-J^−/− pDCs were intranasally transferred to the airways of ovalbumin-sensitized recipient mice. Lung samples of all mice were subjected to tests for histopathology, cytokine profile of bronchoalveolar lavage fluid, airway hyperactivity and expression of T helper type 1 (Th1)/Th2 cells, regulatory T cells and type 2 innate lymphoid cells (ILC2s). The results showed that pDCs with and without RBP-J deficiency significantly differed in expression levels of cluster of differentiation 83 (CD83), but not CD80, CD86 and major histocompatibility complex class II. Co-culturing pDCs with naïve T cells revealed a poorer immunosuppressive effect of RBP-J^−/− pDCs. This may be attributed to the lower expression levels of inducible co-stimulator ligand and lower production of interleukin 10 in RBP-J^−/− pDCs than in control pDCs, which impeded T cell activation and Treg suppression. RBP-J^−/− pDCs were associated with high ILC2 expression and severe Th2 immune responses and airway inflammation. Therefore, Notch signalling is critical for pDC-dependent immunoregulation, and RBP-J deficiency reduces pDC-based immunosuppression via T cell activation and Th cell differentiation. Thus, this pathway may be a therapeutic target for pDC-based anti-asthma immunotherapy.     

Irg1/itaconate metabolic pathway is a crucial determinant of dendritic cells immune-priming function and contributes to resolute allergen-induced airway inflammation

Itaconate is produced from the mitochondrial TCA cycle enzyme aconitase decarboxylase (encoded by immune responsive gene1; Irg1) that exerts immunomodulatory function in myeloid cells. However, the role of the Irg1/itaconate pathway in dendritic cells (DC)-mediated airway inflammation and adaptive immunity to inhaled allergens, which are the primary antigen-presenting cells in allergic asthma, remains largely unknown. House dust mite (HDM)-challenged Irg1^?/? mice displayed increases in eosinophilic airway inflammation, mucous cell metaplasia, and Th2 cytokine production with a mechanism involving impaired mite antigen presentations by DC. Adoptive transfer of HDM-pulsed DC from Irg1-deficient mice into naïve WT mice induced a similar phenotype of elevated type 2 airway inflammation and allergic sensitization. Untargeted metabolite analysis of HDM-pulsed DC revealed itaconate as one of the most abundant polar metabolites that potentially suppress mitochondrial oxidative damage. Furthermore, the immunomodulatory effect of itaconate was translated in vivo, where intranasal administration of 4-octyl itaconate 4-OI following antigen priming attenuated the manifestations of HDM-induced airway disease and Th2 immune response. Taken together, these data demonstrated for the first time a direct regulatory role of the Irg1/itaconate pathway in DC for the development of type 2 airway inflammation and suggest a possible therapeutic target in modulating allergic asthma.     

Chronic schistosomiasis during pregnancy epigenetically reprograms T‐cell differentiation in offspring of infected mothers

Schistosomiasis is a nontransplacental helminth infection. Chronic infection during pregnancy suppresses allergic airway responses in offspring. We addressed the question whether in utero exposure to chronic schistosome infection (Reg phase) in mice affects B‐cell and T‐cell development. Therefore, we focused our analyses on T‐cell differentiation capacity induced by epigenetic changes in promoter regions of signature cytokines in offspring. Here, we show that naïve T cells from offspring of schistosome infected female mice had a strong capacity to differentiate into T_H1 cells, whereas T_H2 differentiation was impaired. In accordance, reduced levels of histone acetylation of the IL‐4 promoter regions were observed in naïve T cells. To conclude, our mouse model revealed distinct epigenetic changes within the naïve T‐cell compartment affecting T_H2 and T_H1 cell differentiation in offspring of mothers with chronic helminth infection. These findings could eventually help understand how helminths alter T‐cell driven immune responses induced by allergens, bacterial or viral infections, as well as vaccines.     

Flagellin Alleviates Airway Allergic Response by Stabilizing Eosinophils through Modulating Oxidative Stress

Eosinophil (Eo) degranulation plays a central role in the initiations of allergic attacks. Flagellin (FGN), the major component of bacterial flagella, has immune regulatory functions. This study aims to investigate the role of FGN in alleviating the allergic reaction by stabilizing Eos. A toll-like receptor 5-knockout mouse strain was employed to test the role of FGN in stabilizing Eos. An airway allergy mouse model was developed to test the administration of FGN in alleviating the airway allergy by stabilizing Eos. The results showed that FGN was required in stabilizing Eos in the airway tissues. FGN prevented specific antigen-induced Eo activation. Oxidative stress was associated with the antigen-induced Eo activation that could be counteracted by the presence of FGN. The FGN levels were lower and chymase levels were higher in the airway tissues of mice with allergic inflammation. Negative correlation was detected between the data of FGN and chymase in the lung tissues. Chymase physically contacted FGN to speed up its degradation. The administration of FGN alleviated experimental allergic inflammation in the mouse airways by stabilized Eos in the lung tissues. In conclusion, FGN contributes to Eo stabilization. The administration of FGN alleviates the experimental airway allergy. The data suggest that FGN can be a candidate to be employed in the treatment of allergic disorders.     

Effects of various anti-asthmatic agents on mite allergen-pulsed murine bone marrow-derived dendritic cells

Background Dendritic cells (DCs) play an important role in the immune response and are critically involved in asthma. β₂‐agonists could potentially exacerbate type 2 T helper (Th2) cell‐mediated immune response. Objectives To determine the effects of various anti‐asthmatic agents on DCs function both in vitro and in vivo. Methods Murine bone marrow‐derived DCs were pulsed with mite allergen in the presence of pranlukast, salbutamol, salmeterol or fluticasone. These DCs were then inoculated intranasally into naïve mice to induce allergic airway inflammation in vivo. Results Pranlukast reduced IL‐10 and increased IL‐12, while fluticasone reduced both IL‐10 and IL‐12 production by mite allergen‐pulsed DCs. Allergic airway inflammation in pranlukast‐ and fluticasone‐treated and mite allergen pulsed DCs‐harbouring mice was attenuated and such response was associated with inhibition of Th2 response in the airway. Salbutamol did not alter cytokine production, while salmeterol reduced IL‐12 production by mite allergen‐pulsed DCs. Lung pathology in β₂‐agonist‐harbouring mice was comparable with those of mite allergen‐pulsed DCs‐harbouring mice. Conclusions Our results indicate that leukotriene receptor antagonists and corticosteroids inhibit DCs‐induced Th2 skewed immune response, and that short‐ and long‐acting β₂‐agonists do not modify DCs‐induced allergic airway inflammation.     

Effect of ozone exposure on allergic sensitization and airway inflammation induced by dendritic cells

BACKGROUND: Epidemiological studies suggest that ozone exposure is related to increased asthma symptoms. Dendritic cells (DCs) are the principal antigen-presenting cells in the airways. OBJECTIVE: We have examined whether ambient doses of ozone (100 ppb for 2 h) enhance allergic sensitization and/or airway inflammation in a mouse model. METHODS: C57BL/6 mice were sensitized to inhaled ovalbumin (OVA) by intratracheal instillation of OVA-pulsed DCs on day 0. Daily exposure to OVA aerosol on days 14-20 resulted in an eosinophilic airway inflammation, as reflected in bronchoalveolar lavage fluid and lung histology. In a first experiment, mice were exposed to ozone or room air immediately prior to and following sensitization. Subsequently, we tested the effect of ozone exposure during antigen challenge in DC-sensitized mice. RESULTS: Exposure to ozone during sensitization did not influence airway inflammation after subsequent allergen challenge. In contrast, in sensitized mice, challenge with OVA together with ozone (days 14-20) resulted in enhanced airway eosinophilia and lymphocytosis, as compared with mice exposed to OVA and room air (1.91 x 106 +/- 0.46 x 106 vs. 0.16 x 106 +/- 0.06 x 106 eosinophils/mL lavage fluid; P = 0.015; 0.49 x 106 +/- 0.11 x 106 vs. 0.08 x 106 +/- 0.03 x 106 lymphocytes/mL lavage fluid; P = 0.004). Ozone exposure without subsequent OVA exposure did not cause airway inflammation. CONCLUSION: Ozone exposure does not increase allergic sensitization but enhances antigen-induced airway inflammation in mice that are sensitized via the airways.     

Experimental gastrointestinal allergy enhances pulmonary responses to specific and unrelated allergens

BACKGROUND: Gastrointestinal allergy often precedes or coexists with respiratory allergy. OBJECTIVE: We hypothesized that established experimental gastrointestinal allergy would prime for the development of allergic respiratory responses. METHODS: BALB/c mice were sensitized with ovalbumin (OVA) in the presence of aluminum potassium sulfate and then subjected to intragastric saline or OVA challenges. After the development of allergen-induced gastrointestinal allergy, mice were intranasally exposed to either saline, OVA, or a neoaeroallergen house dust mite (HDM) extract. Airway inflammation (eg, bronchoalveolar lavage fluid cellularity, cytokine levels, and OVA-specific antibody levels) and airway responsiveness to methacholine exposure were assessed after intranasal allergen exposure. RESULTS: A single intranasal exposure to OVA induced significantly more airway inflammation in intragastric OVA-challenged mice compared with that seen in intragastric saline-treated mice. Kinetic analysis revealed that the observed amplification of lung inflammation was sustained for up to 12 days after the last intragastric OVA challenge after resolution of blood eosinophilia. When mice with gastrointestinal allergy were repeatedly challenged with HDM in the respiratory tract, they experienced enhanced airway inflammation, including bronchoalveolar lavage fluid eosinophilia and increased IL-13 levels. CONCLUSION: Taken together, our results demonstrate that OVA-induced gastrointestinal allergy enhances not only allergic airway responses to OVA but also to HDM, an unrelated aeroallergen. CLINICAL IMPLICATIONS: Experimental gastrointestinal allergy primes for responses to allergens in the respiratory tract, enhancing antigen-specific antibody and T(H)2 cytokine production, airway inflammation, and airway hyperresponsiveness.     

Cholera toxin B suppresses allergic inflammation through induction of secretory IgA

In healthy individuals, humoral immune responses to allergens consist of serum IgA and IgG4, whereas cellular immune responses are controlled by regulatory T (Treg) cells. In search of new compounds that might prevent the onset of allergies by stimulating this type of immune response, we have focused on the mucosal adjuvant, cholera toxin B (CTB), as it induces the formation of Treg cells and production of IgA. Here, we have found that CTB suppresses the potential of dendritic cells to prime for Th2 responses to inhaled allergen. When we administered CTB to the airways of naïve and allergic mice, it strongly suppressed the salient features of asthma, such as airway eosinophilia, Th2 cytokine synthesis, and bronchial hyperreactivity. This beneficial effect was only transferable to other mice by transfer of B but not of T lymphocytes. CTB caused a transforming growth factor-β-dependent rise in antigen-specific IgA in the airway luminal secretions, which was necessary for its preventive and curative effect, as all effects of CTB were abrogated in mice lacking the luminal IgA transporting polymeric Ig receptor. Not only do these findings show a novel therapeutic avenue for allergy, they also help to explain the complex relationship between IgA levels and risk of developing allergy in humans.     

Helminth‐induced CD19+CD23hi B cells modulate experimental allergic and autoimmune inflammation

Numerous population studies and experimental models suggest that helminth infections can ameliorate immuno‐inflammatory disorders such as asthma and autoimmunity. Immunosuppressive cell populations associated with helminth infections include Treg and alternatively‐activated macrophages. In previous studies, we showed that both CD4⁺CD25⁺ Treg, and CD4^– MLN cells from Heligmosomoides polygyus‐infected C57BL/6 mice were able to transfer protection against allergic airway inflammation to sensitized but uninfected animals. We now show that CD4^–CD19⁺ MLN B cells from infected, but not naïve, mice are able to transfer a down‐modulatory effect on allergy, significantly suppressing airway eosinophilia, IL‐5 secretion and pathology following allergen challenge. We further demonstrate that the same cell population can alleviate autoimmune‐mediated inflammatory events in the CNS, when transferred to uninfected mice undergoing myelin oligodendrocyte glycoprotein_(p35–55)‐induced EAE. In both allergic and autoimmune models, reduction of disease was achieved with B cells from helminth‐infected IL‐10^?/? donors, indicating that donor cell‐derived IL‐10 is not required. Phenotypically, MLN B cells from helminth‐infected mice expressed uniformly high levels of CD23, with follicular (B2) cell surface markers. These data expand previous observations and highlight the broad regulatory environment that develops during helminth infections that can abate diverse inflammatory disorders in vivo.     

Allergen‐specific naïve and memory CD4+ T cells exhibit functional and phenotypic differences between individuals with or without allergy

Although allergen‐specific CD4⁺ T cells are detectable in the peripheral blood of both individuals with or without allergy, their frequencies and phenotypes within the memory as well as naïve repertoires are incompletely known. Here, we analyzed the DRB1*0401‐restricted responses of peripheral blood‐derived memory (CD4⁺CD45RO⁺) and naïve (CD4⁺CD45RA⁺) T cells from subjects with or without allergy against the immunodominant epitope of the major cow dander allergen Bos d 2 by HLA class II tetramers in vitro. The frequency of Bos d 2_127–142‐specific memory T cells in the peripheral blood‐derived cultures appeared to be higher in subjects with allergy than those without, whereas naïve Bos d 2_127–142‐specific T cells were detectable in the cultures of both groups at nearly the same frequency. Surprisingly, the TCR avidity of Bos d 2_127–142‐specific T cells of naïve origin, as assessed by the intensity of HLA class II tetramer staining, was found to be higher in individuals with allergy. Upon restimulation, long‐term Bos d 2_127–142‐specific T‐cell lines generated from both memory and naïve T‐cell pools from individuals with allergy proliferated more strongly, produced more IL‐4 and IL‐10, and expressed higher levels of CD25 but lower levels of CXCR3 than the T‐cell lines from individuals without allergy, demonstrating differences also at the functional level. Collectively, our current results suggest that not only the memory but also the naïve allergen‐specific T‐cell repertoires differ between individuals with or without allergy.