Genes of tolerance

The Therapeutic Effect of Traditional LiuJunZi Decoction on Ovalbumin-Induced Asthma in Balb/C Mice

Aim

To investigate the therapeutic effect of LiuJunZi decoction (LJZD) in an experimental model of asthma and uncover its potential mechanism.

Materials and Methods

The ovalbumin (OVA) was applied to induce asthma in Balb/C mice, and LJZD was orally administrated to asthmatic mice. The lung function and histological lesion were evaluated by airway hyperresponsiveness assay, lung edema assay, and hematoxylin and eosin staining. The amounts of CD4⁺CD25⁺Foxp3⁺ T_Reg cells were analyzed through combining fluorescent antibody staining with flow cytometry assay. The levels of inflammatory factors and immunoglobulins were detected by enzyme-linked immuno sorbent assay (ELISA). The expression of miR-21 and miR-146a was investigated by real-time PCR. The protein expression of activating protein-1 (AP-1), nuclear factor kappa-B (NF-κB), and NF-κB inhibitor alpha (IκBα) was determined by western blotting.

Results

LJZD improves OVA-induced asthma in Balb/C mice, which is manifested by decreasing lung edema, Penh levels, lung histological lesion, and inflammatory cell infiltration. LJZD increased the number of CD4⁺CD25⁺Foxp3⁺ T_Reg cells in blood mononuclear cells from asthmatic mice. Furthermore, LJZD reduced the levels of tumor necrosis factor-α (TNF-α), interleukin- (IL-) 4, IL-6, IgG1, and IgE, but increased interferon gamma (IFN-γ) expression, in serum of asthmatic mice, and also decreased the expression of IL-17a, IL-23, IL-25, and thymic stromal lymphopoietin (Tslp) in lung tissues. In addition, miR-21 and miR-146a expression and phospho (p)-NF-κB, p-IκBα, and AP-1 protein expression were inhibited by LJZD in lung tissues from asthmatic mice.

Conclusion

LJZD improved OVA-induced asthma in Balb/C mice by inhibiting allergic inflammation and Th2 immunoreaction, which might be associated with the inactivation of the NF-κB signaling pathway.

Evidence for Asthma in the Lungs of Mice Inoculated with Different Doses of Toxocara canis

Toxocara canis, a common roundworm that mainly causes toxocariasis, is a zoonotic parasite found worldwide. Humans, an accidental host, can acquire T. canis infection through accidental ingestion of T. canis-embryonated egg-contaminated food, water, and soil, and by encapsulated larvae in a paratenic host's viscera or meat. Long-term residence of T. canis larvae in a paratenic host's lungs may induce pulmonary inflammation that contributes to lung injury, airway inflammatory hyperresponsiveness, and collagen deposition in mice and clinical patients. This study intended to investigate the relationship between T. canis infection and allergic asthma in BALB/c mice inoculated with high, moderate, and low doses of T. canis eggs for a 13-week investigation. The airway hyperresponsiveness (AHR) to methacholine, collagen deposition, cytokine levels, and pathological changes in lung tissues was assessed in infected mice at weeks 1, 5, and 13 postinfection. The cell composition in bronchoalveolar lavage fluid of infected mice was assessed at weeks 5 and 13 postinfection. Compared with uninfected control mice, all groups of T. canis-infected mice exhibited significant AHR, a dose-dependent increase in eosinophilic infiltration leading to multifocal interstitial and alveolar inflammation with abundant mucus secretion, and collagen deposition in which the lesion size increased with the infective dose. Infected mice groups also showed significant expressions of eotaxin and type 2 T-helper-dominant cytokines such as interleukin (IL)-4, IL-5, and IL-13. Overall, these results suggest that T. canis larval invasion of the lungs may potentially cause pulmonary inflammatory injury and could subsequently contribute to the development of allergic manifestations such as asthma.

Nanoparticle-allergen complexes for allergen immunotherapy

Allergen-specific immunotherapy was introduced in clinical settings more than 100 years ago. It remains the only curative approach to treating allergic disorders that ameliorates symptoms, reduces medication costs, and blocks the onset of new sensitizations. Despite this clinical evidence and knowledge of some immunological mechanisms, there remain some open questions regarding the safety and efficacy of this treatment. This suggests the need for novel therapeutic approaches that attempt to reduce the dose and frequency of treatment administration, improving patient compliance, and reducing costs. In this context, the use of novel adjuvants has been proposed and, in recent years, biomedical applications using nanoparticles have been exploited in the attempt to find formulations with improved stability, bioavailability, favorable biodistribution profiles, and the capability of targeting specific cell populations. In this article, we review some of the most relevant regulatory aspects and challenges concerning nanoparticle-based formulations with immunomodulatory potential, their related immunosafety issues, and the nature of the nanoparticles most widely employed in the allergy field. Furthermore, we report in vitro and in vivo data published using allergen/nanoparticle systems, discuss their impact on the immune system in terms of immunomodulatory activity and the reduction of side effects, and show that this strategy is a novel and promising tool for the development of allergy vaccines.

Mechanisms of Aeroallergen Immunotherapy: Subcutaneous Immunotherapy and Sublingual Immunotherapy

Allergen immunotherapy (AIT) is an effective way to treat allergic disorders, targeting the underlying mechanisms and altering the disease course by inducing a long-lasting clinical and immune tolerance to allergens. Although sublingual and subcutaneous routes are used in daily practice, many novel ways to decrease side effects and duration and increase efficacy have been pursued. Further studies are needed to develop biomarkers for the identification of AIT responder patients and also to use the developed knowledge in allergy prevention studies. Future directions in AIT include treatments for autoimmune diseases, chronic infections, organ transplantation, and breaking immune tolerance to cancer cells.

Anti-allergic effect of α-cubebenoate isolated from Schisandra chinensis using in vivo and in vitro experiments

AIM OF THE STUDY

In Oriental countries, the dried fruits of Schisandra chinensis are extensively used in traditional medicine to treat asthma, gonorrhea, and other diseases. Recently, α-cubebenoate was isolated as an anti-inflammatory component from Schisandra chinensis. In the present study, the authors examined the anti-allergic effect of α-cubebenoate using in vivo and in vitro experiments.

MATERIALS AND METHODS

α-Cubebenoate was isolated from an extract of Schisandra chinensis fruits. Antigen-induced degranulation and Ca(2+) mobilization were measured in RBL-2H3 mast cells. In addition, BALB/c mice were sensitized with ovalbumin and aluminum hydroxide, and then challenged with ovalbumin for three consecutive days. α-Cubebenoate (1mg/kg) was administered intraperitoneally 30min before each ovalbumin challenge.

RESULTS

In RBL-2H3 mast cells, α-cubebenoate inhibited antigen-induced degranulation and increase of intracellular Ca(2+) concentrations. In the ovalbumin-induced asthma model, α-cubebenoate suppressed bronchiolar structural changes induced by ovalbumin challenge. Furthermore, α-cubebenoate strongly inhibited accumulations of eosinophils, macrophages, and lymphocytes in bronchoalveolar lavage fluid. α-Cubebenoate also suppressed Th2 cytokines (IL-4 and IL-13) and TGF-β1 in lung tissues and in immune cells at the mRNA and protein levels.

CONCLUSION

α-Cubebenoate has an inhibitory effect on allergic inflammation and could be utilized as an agent for the treatment of asthma.

Zerumbone enhances the Th1 response and ameliorates ovalbumin-induced Th2 responses and airway inflammation in mice

Zerumbone is a sesquiterpene compound isolated from the rhizome of wild ginger, Zingiber zerumbet Smith. The rhizomes of the plant are used as a spice and traditional medicine. Zerumbone was shown to possess anticarcinogenic, anti-inflammatory, and antioxidant properties. However, the antiallergic activity and the underlying mechanism of zerumbone have not been reported. Herein, we investigated the immunomodulatory effects of zerumbone on antigen-presenting dendritic cells (DCs) in vitro and its potential therapeutic effects against ovalbumin (OVA)-induced T helper 2 (Th2)-mediated asthma in mice. In the presence of zerumbone, lipopolysaccharide-activated bone marrow-derived DCs enhanced T cell proliferation and Th1 cell polarization in an allogeneic mixed lymphocyte reaction. In animal experiments, mice were sensitized and challenged with OVA, and were orally treated with different doses of zerumbone after sensitization. Circulating titers of OVA-specific antibodies, airway hyperresponsiveness to methacholine, histological changes in lung tissues, the cell composition and cytokine levels in bronchoalveolar lavage fluid, and cytokine profiles of spleen cells were assessed. Compared to OVA-induced hallmarks of asthma, oral administration of zerumbone induced lower OVA-specific immunoglobulin E (IgE) and higher IgG2a antibody production, attenuated airway hyperresponsiveness, prevented eosinophilic pulmonary infiltration, and ameliorated mucus hypersecretion. Zerumbone treatment also reduced the production of eotaxin, keratinocyte-derived chemokine (KC), interleukin (IL)-4, IL-5, IL-10, and IL-13, and promoted Th1 cytokine interferon (IFN)-γ production in asthmatic mice. Taken together, these results suggest that zerumbone exhibits an antiallergic effect via modulation of Th1/Th2 cytokines in an asthmatic mouse model.

Mechanisms of immune tolerance to allergens in children

Because the prevalence of allergic diseases has significantly increased in recent years, understanding the causes and mechanisms of these disorders is of high importance, and intense investigations are ongoing. Current knowledge pinpoints immune tolerance mechanisms as indispensable for healthy immune response to allergens in daily life. It is evident that development and maintenance of allergens-pecific T cell tolerance is of vital importance for a healthy immune response to allergens. Such tolerance can be gained spontaneously by dose-dependent exposures to allergens in nature or by allergen-specific immunotherapy. Allergen-specific immunotherapy induces regulatory T cells with the capacity to secrete interleukin-10 and transforming growth factor-β, limits activation of effector cells of allergic inflammation (such as mast cells and basophils), and switches antibody isotype from IgE to the noninflammatory type IgG4. Although allergen-specific immunotherapy is the only method of tolerance induction in allergic individuals, several factors, such as long duration of treatment, compliance problems, and life-threatening side effects, have limited widespread applicability of this immunomodulatory treatment. To overcome these limitations, current research focuses on the introduction of allergens in more efficient and safer ways. Defining the endotypes and phenotypes of allergic diseases might provide the ability to select ideal patients, and novel biomarkers might ensure new custom-tailored therapy modalities.

Effects of taraxasterol on ovalbumin-induced allergic asthma in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Taraxasterol was isolated from the Chinese medicinal herb Taraxacum officinale which has been frequently used as a remedy for inflammatory diseases. In the present study, we determined the in vivo protective effect of taraxasterol on allergic asthma induced by ovalbumin (OVA) in mice.

MATERIALS AND METHODS

Mice were sensitized and challenged with OVA, and were orally treated daily with taraxasterol at 2.5, 5 and 10mg/kg from day 23 to 27 after sensitization. The number of inflammatory cells in bronchoalveolar lavage fluid (BALF) was determined. Th2 cytokine interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-13 (IL-13) production in BALF and OVA-specific immunoglobulin E (IgE) production in sera were measured using ELISA. Histological changes in lung tissues were examined using hematoxylin and eosin (H&E) and periodic acid-Schiff staining (PAS). Airway hyperresponsiveness (AHR) to inhaled methacholine was assessed.

RESULTS

Taraxasterol dramatically decreased the total inflammatory cell and main inflammatory cell counts, reduced the production of Th2 cytokine IL-4, IL-5, IL-13 in BALF and OVA-specific IgE in sera, and suppressed AHR in a dose-dependent manner. Histological studies demonstrated that taraxasterol substantially suppressed OVA-induced inflammatory cells infiltration into lung tissues and goblet cell hyperplasia in airways.

CONCLUSIONS

This finding suggests that taraxasterol protects against OVA-induced allergic asthma in mice.

Innate and adaptive immune responses to the major Parietaria allergen Par j 1 in healthy subjects

In this study we wanted to analyse the pattern of the immune response to the Parietaria major allergen Par j 1 in freshly purified peripheral blood mononuclear cell (PBMC) from healthy subjects. We observed that Par j 1 was capable of inducing IFN-γ production by CD3⁻ and CD16⁺/CD56⁺ cells exclusively in healthy individuals. Furthermore, a multiparametric analysis allowed us a better definition of two IFN-γ-Par j 1 specific populations (IFN-γ(dim) and IFN-γ(high)) characterized by the presence of different proportions of NKT and NK cells. We also identified the concomitant presence of a subset of IL-10⁺ NK cells. Moreover, CFSE staining showed that the Par j 1 preferentially induced the proliferation of CD3⁻/CD56⁺/CD335⁺ cells. Finally, a subset of CD4⁺/CD25⁺/FoxP3⁺/IL-10⁻ T cells was identified. The result of this pilot study suggest that during a tolerogenic response, the major allergen of the Parietaria pollen works as an activator of both the innate and the adaptive human immune system.

Serum levels of interleukin-13 and interferon-gamma from adult patients with asthma in Mysore

Serum protein analysis for noninvasive quantification of airway inflammation in asthma is a promising research tool in the field of lung diseases. Cytokines are believed to have major role in inflammatory process of the airways of the lung. There is an imbalance between T-helper (Th)-2 cells, which secrete interleukin (IL)-4 and interleukin (IL)-13, and Th1 cells, which secrete interferon (IFN)-gamma in asthma. To test the hypothesis that serum IL-13 and IL-4 levels may be elevated whereas IFN-gamma would be decreased in this cohort of patients, a property that could make them possible candidate biomarkers in determining asthma occurrence and severity, we measured concentrations of IL-4, IL-13 and IFN-gamma in serum samples of 88 subjects (44 normal, 12 with mild asthma, 16 with moderate asthma, and 16 with severe asthma). Serum Levels of IL-4, IL-13, and IFN-gamma were determined by an enzyme-linked immune-sorbent assay (ELISA). Median serum level of IFN-gamma in asthmatic patients was 8.0 pg/ml, while it was 11.4 pg/ml in healthy controls. However, the difference was not significant. Among the different age groups in whom IFN-gamma was assessed, the highest median value in both cases and controls was observed in the age group of 31-40 years. The median serum level of IL-13 was 40.0 pg/ml in asthmatic patients and 58.25 pg/ml in healthy controls. The difference was not significant. On subgroup analysis, no significant difference of IFN-gamma and IL-13 between asthma of different severities was observed. The study also revealed nonsignificant difference of serum cytokines with the duration of asthma, number of allergens, and severity of sensitization. Normal serum levels of IFN-gamma and IL-13 in asthmatic patients suggest their neutral role in the inflammatory process; however, more studies are required to establish the effect of these cytokines in adulthood asthma in different ethnic populations.

Polyopes affinis alleviates airway inflammation in a murine model of allergic asthma

Marine algae have been utilized in food as well as medicine products for a variety of purposes. The purpose of this study was to determine whether an ethanol extract of Polyopes affinis (P.affinis) can inhibit the pathogenesis of T helper 2 (Th2)-mediated allergen-induced airway inflammation in a murine model of asthma. Mice that were sensitized and challenged with ovalbumin (OVA) evidenced typical asthmatic reactions such as the following: an increase in the number of eosinophils in the bronchoalveolar lavage (BAL) fluid; a marked influx of inflammatory cells into the lung around blood vessels and airways as well as the narrowing of the airway luminal; the development of airway hyperresponsiveness (AHR); the presence of pulmonary Th2 cytokines; and the presence of allergenspecific immunoglobulin E (IgE) in the serum. The successive intraperitoneal administration of P. affinis ethanolic extracts before the last airway OVA-challenge resulted in a significant inhibition of all asthmatic reactions. These data suggest that P. affinis ethanolic extracts possess therapeutic potential for the treatment of pulmonary allergic disorders such as allergic asthma.

99th Dahlem conference on infection, inflammation and chronic inflammatory disorders: farm lifestyles and the hygiene hypothesis

About 15 years have gone by since Strachan first proposed the idea that infections and unhygienic contact may confer protection from the development of allergic illnesses. The so-called 'hygiene hypothesis' has since undergone numerous modifications in the field of epidemiology, clinical science and immunology. Three main areas of research have been brought forward: to explore the role of overt viral and bacterial infections for the inception of allergic diseases; to investigate the significance of environmental exposure to microbial compounds on the development of allergies; and to study the effect of both exposures on underlying innate and adaptive immune responses. A concept unifying these various aspects has not been found, but various pieces of a complex interplay between immune responses of the host, characteristics of the invading microorganism, the level and variety of the environmental exposure and the interactions between an exposed subject's genetic background and the environmental exposures becomes apparent. A natural experiment relating to the hygiene hypothesis is the recurrent observation of a protective effect of growing up on a farm for asthma and allergies. This has been shown in a large number of epidemiological studies across the world among children and adults. The timing and duration of exposure are likely to play a critical role. The largest reduction in risk has been demonstrated for those exposed prenatally and continuously thereafter until adulthood. The protective factors in these farming environments have not been unravelled completely. Findings from various studies suggest that the contact with farm animals, at least in childhood, confers protection. Also the consumption of unprocessed cow's milk directly from the farm has been shown to protect from childhood asthma and allergies. Increased levels of microbial substances may, at least in part, contribute to the 'farm effect'. However, only few studies have measured microbial exposures in these environments and the results obtained so far suggest that the underlying protective microbial exposure(s) have not been identified, but a number of studies using metagenomic approaches are currently under way. The mechanisms by which such environmental exposures confer protection from respiratory allergies are also not well understood. There is good evidence for the involvement of innate immune responses, but translation into protective mechanisms for asthma and allergies is lacking. Furthermore, a number of gene x environment interactions have been observed.

Tolerance induction after specific immunotherapy with pollen allergoids adjuvanted by monophosphoryl lipid A in children

Specific immunotherapy (SIT) is a well-established and clinically effective treatment for allergic diseases. A pollen allergoid formulated with the T helper type 1 (Th1)-inducing adjuvant monophosphoryl lipid A (MPL) facilitates short-term SIT. Little is known about mechanisms of tolerance induction in this setting. In a prospective study, 34 patients allergic to grass pollen (25 male, nine female, median age 10.2 years) received a total of 44 SIT courses (20 in the first, 24 in the second) with MPL-adjuvanted pollen allergoids. Immunogenicity was measured by levels of specific immunoglobulin G (IgG(grass)) and IgG4(grass) by antibody blocking properties on basophil activation, and by induction of CD4(+), CD25(+) and forkhead box P3 (FoxP3(+)) regulatory T cells (T(reg)). Specific IgG and IgG4 levels increased only slightly in the first year of SIT. In the second year these changes reached significance (P < 0.0001). In keeping with these findings, we were able to show an increase of T(reg) cells and a decreased release of leukotrienes after the second year of treatment. In the first year of treatment we found little evidence for immunological changes. A significant antibody induction was seen only after the second course of SIT. Short-course immunotherapy with pollen allergoids formulated with the Th1-inducing adjuvant MPL needs at least two courses to establish tolerance.

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-beta-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.

Humoral and cellular immune responses to Blomia tropicalis and concanavalin A-binding fractions in atopic patients

Blomia tropicalis, Dermatophagoides pteronyssinus and D. farinae are prevalent house dust mites. Concanavalin A-binding components derived from B. tropicalis (Bt-ConA extract) are highly immunogenic in allergic diseases. The aim of the present study was to evaluate the humoral and cellular immune responses to B. tropicalis in mite-sensitized patients. A total of 137 patients with allergic rhinitis with/without asthma and 109 non-atopic subjects were selected and analyzed by the skin prick test, and for total serum IgE and specific IgE levels to both Bt-total and Bt-ConA extracts, their proliferative response and cytokine (IFN-gamma and IL-5) production by peripheral blood mononuclear cells (PBMC) stimulated with both extracts. Skin prick test showed that 70% of the patients were sensitized to Bt (Bt+) and similar levels of specific IgE to Bt-total and Bt-ConA extracts were demonstrable in Bt+ patients. Significant PBMC proliferation was observed in response to Bt-total extract in Bt+, but not in Bt- patients and non-atopic subjects (P < 0.001). Bt-ConA extract induced increased proliferative responses in all patient groups compared to medium alone (P < 0.05), but these responses were significantly decreased in the presence of the mannopyranoside ConA inhibitor (P < 0.05). Significant IFN-gamma production was observed after Bt-ConA stimulation of Bt+ patients (P < 0.05), while Bt-total extract had no effect. IL-5 production was consistently detected in Bt+ patients after allergen-specific stimulation or with no stimulus, indicating that PBMC from allergic patients are prone to produce Th2 profile cytokines, spontaneously or inductively by allergen restimulation. These data showed that ConA-binding components isolated from B. tropicalis may contain relevant antigens that are involved in both humoral and cellular immune responses. However, without an additional purification procedure to eliminate the residual contamination with ConA, its use in immunotherapeutic procedures cannot be recommended.

Mechanisms and treatment of allergic disease in the big picture of regulatory T cells

Various populations of regulatory T (Treg) cells have been shown to play a central role in the maintenance of peripheral homeostasis and the establishment of controlled immune responses. Their identification as key regulators of immunologic processes in peripheral tolerance to allergens has opened an important era in the prevention and treatment of allergic diseases. Both naturally occurring CD4+CD25+ Treg cells and inducible populations of allergen-specific, IL-10-secreting Treg type 1 (T(R)1) cells inhibit allergen-specific effector cells in experimental models. Skewing of allergen-specific effector T cells to a regulatory phenotype appears to be a key event in the development of healthy immune response to allergens and successful outcome in allergen-specific immunotherapy. Forkhead box protein 3-positive CD4+CD25+ Treg cells and T(R)1 cells contribute to the control of allergen-specific immune responses in several major ways, which can be summarized as suppression of dendritic cells that support the generation of effector T cells; suppression of effector T(H)1, T(H)2, and T(H)17 cells; suppression of allergen-specific IgE and induction of IgG4; suppression of mast cells, basophils, and eosinophils; interaction with resident tissue cells and remodeling; and suppression of effector T-cell migration to tissues. Current strategies for drug development and allergen-specific immunotherapy exploit these observations, with the potential for preventive therapies and cure for allergic diseases.

Are we getting enough allergens?

This paper proposes that reduced allergen exposure is one of the factors underlying the higher risk of IgE-mediated allergic disease in populations with an urbanized, westernized, and affluent lifestyle. This lower allergen exposure results in the failure to induce and maintain immune tolerance to common environmental allergens. The paper summarizes different lines of evidence that may support or contradict this hypothesis and points to areas where more knowledge is needed.

The genetic and environmental basis of atopic diseases

The prevalence of atopic diseases has increased abruptly in recent years in most Westernized societies, making the question why this happened the topic of a heated debate. The best paradigm available to date to explain this steep rise, the 'hygiene hypothesis', supports that it is the excess 'cleanliness' of our environments that has led to the decline in the number of infectious stimuli that are necessary for the proper development of our immune system. Recent findings support that it is the combined effect that not only pathogenic, but also non-pathogenic microorganisms, and even their structural components,can exert on the immune system that deters from the development of atopic responses. Adding to these results are intriguing new findings on the effect different gene polymorphisms can have on an individual's predisposition to allergic diseases. The most important linkages produced, to date, include those among the genes for IL-4, IL-13, HLA-DRB, TNF, LTA,FCER1B, IL-4RA, ADAM33, TCR alpha/delta, PHF11, GPRA, TIM, p40, CD14, DPP10, T-bet, GATA-3, and FOXP3 and allergic disorders. The two parallel research efforts, epidemiologic and genetic, are only recently starting to converge,producing fascinating results on the effect particular gene-environment interactions might have in the development of atopy.The most important lesson learned through this tremendous research effort is that not only a small number but thousands and millions of separate risk factors act in concordance in the production of the allergic phenotype.

[Regulatory cells]

The role of regulatory T cells in the induction and maintenance of peripheral tolerance has received growing attention during the last years. Several subsets of regulatory T cells were described based on their surface markers and cytokine production, but nevertheless, there are no specific markers for any subsets and their classification relies on their suppression mechanism. It is unknown which of the subgroups of regulatory T cells is more important in the prevention and control of allergic diseases, being commonly accepted its importance in homeostasis.

Ovalbumin modified by gamma irradiation alters its immunological functions and allergic responses

It is well known that gamma (gamma)-ray irradiation results in the alteration of biological function of bioactive materials such as proteins, saccharides and lipids. In this study the effect of gamma-irradiation on the chemical and immunological property of an allergen, ovalbumin (OVA), was investigated. Irradiation of more than 10 kGy resulted in the alteration of the structure of OVA. However, OVA treated with 10 kGy irradiation (10 kGy-OVA), but not 100 kGy-OVA, fully maintained immunological reactivity to a monoclonal antibody specific to the intact allergen (clone 14). Mice immunized with 10 kGy- as well as 100 kGy-OVA showed significantly lower antibody response to the allergen than those with intact OVA in a gamma-ray dosage-dependent manner. Especially immunization of both 10 kGy- and 100 kGy-OVA induced a significant decrease of OVA-specific IgE. Splenocytes of mice immunized with irradiated OVA showed a significant reduction in OVA-specific T cell proliferation and the secretion of Th1-type (IFN-gamma and IL-2) and Th2-type cytokines (IL-4 and IL-6). The expression of T cell activation markers such as CD25 and CD44 was also down-regulated in T cells of mice immunized with irradiated OVAs. These results suggest that gamma-ray irradiation of OVA suppress humoral and cellular immune responses specific to the allergen OVA, and the modification method with gamma-irradiation may be available for the control of allergy.

A hybrid expressing genetically engineered major allergens of the Parietaria pollen as a tool for specific allergy vaccination

BACKGROUND

Allergy is an immunological disorder affecting about 25% of the population living in the industrialized countries. Specific immunotherapy is the only treatment with a long-lasting relief of allergic symptoms and able to reduce the risk of developing new allergic sensitizations and inhibiting the development of clinical asthma in children treated for allergic rhinitis.

METHODS

By means of DNA recombinant technology, we were able to design a head to tail dimer expressing disulphide bond variants of the major allergen of the Parietaria pollen. IgE binding activity was studied by Western blot, ELISA inhibition assays and the skin prick test. T cell recognition was studied by peripheral blood mononuclear cell proliferation. The immunogenicity of the hybrid was studied in a mouse model of sensitization.

RESULTS

In vitro and in vivo analysis showed that the disruption of specific cysteine residues in both allergens caused a strong reduction in IgE binding activity of the PjEDcys hybrid. In addition,we were able to show that a reduction in the IgE epitope content profoundly reduced the anaphylactic activity of the hybrid (from 100 to 1,000 times less than wild-type allergens) without interfering with the T cell recognition. Sera from BALB/c mice immunized with the hybrid were able to bind the natural Parietaria allergens and to inhibit the binding of human IgE to wild-type Par j 1 and Par j 2 allergens up to 90%.

CONCLUSION

Our results demonstrate that hybrid-expressing disulphide bond variants of the major allergens of the Parietaria pollen displayed reduced allergenicity and maintained T cell reactivity for induction of protective antibodies.

Histamine receptors in immune regulation and allergen-specific immunotherapy

The cells involved in the regulation of immune responses and hematopoiesis express histamine receptors and secrete histamine. Histamine acting through four types of its receptors has been shown not only to affect chronic inflammatory responses but also to regulate several essential events in the immune response. Histamine signals have a role in the mechanisms of tolerance induced during allergen-specific immunotherapy (SIT), acting mainly through its receptor (HR) type 2. It positively interferes with the peripheral antigen tolerance induced by T regulatory cells in several pathways. The rationale for the concomitant use of H1 antihistamines during SIT is diverse and includes reduction of its immediate side effects as well as enhancement of mechanisms of specific tolerance and anti-inflammatory effects of vaccination.

Dexamethasone and IL-10 stimulate glucocorticoid-induced leucine zipper synthesis by human mast cells

BACKGROUND

Glucocorticoids (GCs) decrease tissue mast cell (MC) number and prevent their activation via their high-affinity IgE receptor. Glucocorticoid-induced leucine zipper (GILZ) is one of the GC-induced genes, which inhibits the functions of the transcriptional activators AP-1 and NF-kappaB. GILZ appears to be a critical actor in the anti-inflammatory and immunosuppressive effects of GCs in human T lymphocytes, macrophages and dendritic cells.

AIMS OF THE STUDY

We investigated whether GILZ was produced by human MCs and whether GILZ synthesis was stimulated by GCs. We also investigated whether GILZ production was modulated by (i) IL-10, because of its common immunosuppressive properties with GCs, (ii) histamine because of its pro-inflammatory properties and (iii) IL-4 and IL-5 because of their ability to favour MC survival and proliferation with SCF.

METHODS

The human MC lines HMC-1 5C6 and LAD-2, and cord blood-derived MCs (CB-MCs) were cultured alone or in the presence of GCs, IL-10, histamine, IL-4 or IL-5. The expression of GILZ was evaluated by using RT-PCR, Western blotting or immunocytochemistry.

RESULTS

We found that human MC lines and CB-MCs constitutively produce GILZ. We also show that GCs and IL-10 stimulate GILZ production by human MCs. Our present results indicate that histamine, IL-4 and IL-5 alone or in combination with SCF do not downregulate GILZ production by MCs.

CONCLUSIONS

These results show that GCs and IL-10 stimulate GILZ production by human MCs. As GILZ mediates anti-inflammatory effects of GCs in immune cells, we speculate that GILZ could account for the deactivation of MCs by GCs and IL-10.

Mechanisms of allergen specific immunotherapy--T-cell tolerance and more

Specific immune suppression and induction of tolerance are essential processes in the regulation and circumvention of immune defence. The balance between allergen-specific T-regulatory (Treg) cells and T helper 2 cells appears to be decisive in the development of allergic and healthy immune response against allergens. Treg cells consistently represent the dominant subset specific for common environmental allergens in healthy individuals. In contrast, there is a high frequency of allergen-specific T helper 2 cells in allergic individuals. A decrease in interleukin (IL)-4, IL-5 and IL-13 production by allergen-specific CD4+ T cells due to the induction of peripheral T cell tolerance is the most essential step in allergen-specific immunotherapy (SIT). Suppressed proliferative and cytokine responses against the major allergens are induced by multiple suppressor factors, such as cytokines like IL-10 and transforming growth factor (TGF)-beta and cell surface molecules like cytotoxic T lymphocyte antigen-4, programmed death-1 and histamine receptor 2. There is considerable rationale for targeting T cells to increase efficacy of SIT. Such novel approaches include the use of modified allergens produced using recombinant DNA technology and adjuvants or additional drugs, which may increase the generation of allergen-specific peripheral tolerance. By the application of the recent knowledge in Treg cells and related mechanisms of peripheral tolerance, more rational and safer approaches are awaiting for the future of prevention and cure of allergic diseases.

The many faces of the hygiene hypothesis

About 15 years have gone by since Strachan first proposed the idea that infections and unhygienic contact might confer protection against the development of allergic illnesses. The so-called hygiene hypothesis has ever since undergone numerous more or less subtle modifications by various researchers in the fields of epidemiology, clinical science, and immunology. Three major tracts have developed exploring the role of overt viral and bacterial infections, the significance of environmental exposure to microbial compounds, and the effect of both on underlying responses of the innate and adaptive immunity. To date, a truly unifying concept has not yet emerged, but various pieces of a complex interplay between immune responses of the host, characteristics of the invading microorganism, the level and variety of the environmental exposure, and the interactions between a genetic background and a range of exposures becomes apparent. These influences are discussed as determinants for a number of complex allergic illnesses in this review, while we attempt to pay attention to the importance of different phenotypes, namely of the asthma syndrome. Even if today practical implications cannot directly be deduced from these findings, there is great potential for the development of novel preventive and therapeutic strategies in the future.

Future of allergen-specific immunotherapy

Allergen-specific immunotherapy (SIT) has been used for almost a century as a desensitising therapy for allergic diseases. Administration of appropriate concentrations of allergen extracts has been shown to be reproducibly effective when patients are carefully selected. The disadvantage with allergen extracts is that they consist of nonallergenic or even toxic proteins, and can induce severe side effects including anaphylaxis and death. Several strategies have been developed to tackle this issue. With the introduction of recombinant DNA technology and peptide chemistry, it became possible to produce SIT vaccines with reduced allergenic activity. In addition, current understanding of immunological mechanisms of SIT, particularly the role of regulatory T cells in allergen-specific peripheral tolerance, may enable novel treatment strategies.

Immune mechanisms of allergen-specific sublingual immunotherapy

Sublingual immunotherapy has been shown in some clinical studies to modulate allergen-specific antibody responses [with a decrease in the immunoglobulin E/immunoglobulin G4 (IgE/IgG4) ratio] and to reduce the recruitment and activation of proinflammatory cells in target mucosa. Whereas a central paradigm for successful immunotherapy has been to reorient the pattern of allergen-specific T-cell responses in atopic patients from a T helper (Th)2 to Th1 profile, there is currently a growing interest in eliciting regulatory T cells, capable of downregulating both Th1 and Th2 responses through the production of interleukin (IL)-10 and/or transforming growth factor (TGF)-beta. We discuss herein immune mechanisms involved during allergen-specific sublingual immunotherapy (SLIT), in comparison with subcutaneous immunotherapy. During SLIT, the allergen is captured within the oral mucosa by Langerhans-like dendritic cells expressing high-affinity IgE receptors, producing IL-10 and TGF-beta, and upregulating indoleamine dioxygenase (IDO), suggesting that such cells are prone to induce tolerance. The oral mucosa contains limited number of proinflammatory cells, such as mast cells, thereby explaining the well-established safety profile of SLIT. In this context, second-generation vaccines based on recombinant allergens in a native conformation formulated with adjuvants are designed to target Langerhans-like cells in the sublingual mucosa, with the aim to induce allergen-specific regulatory T cells. Importantly, such recombinant vaccines should facilitate the identification of biological markers of SLIT efficacy in humans.

New cohorts of naive T cells exacerbate ongoing allergy but can be suppressed by regulatory T cells

Although as pretreatment oral tolerance is a potent means to achieve systemic suppression, its application in ongoing disease is controversial. Here we propose that availability of naive T cells may critically determine whether immunological tolerance is achieved during ongoing antigenic reactivity. Infusion of naive antigen-specific T cells into mice directly prior to eliciting a secondary Th2 response induces these naive cells to actively engage in the antigenic response despite presence of established memory. Naive antigen-specific T-cells divided faster, produced more interleukin (IL)-2, IL-4 and IL-5 and enhanced immunoglobulin E (IgE) release during a secondary Th2 response, compared with naive T cells that were infused prior to a primary response. Despite such contribution by new cohorts of naive T cells co-infusion of mucosal Tr together with naive T cells could suppress enhanced IgE release during a secondary Th2 response. We conclude that naive T cells contribute to a secondary Th2 response and although they can still be suppressed in the presence of sufficient numbers of mucosal Tr, they may interfere with potential therapeutic application of mucosal tolerance.

Immunotherapy of hypersensitivity to hymenoptera venom

Insect sting allergy is a common condition with a risk of life-threatening anaphylaxis. After a severe reaction, the fear of being restung can significantly reduce quality of life. Venom immunotherapy (VIT) is a highly effective treatment of the underlying type I-sensitisation. This review addresses the mechanisms of immune modulation by VIT and outlines current clinical application. Although highly effective in the majority of patients, VIT fails in a few individuals. It can also cause systemic allergic side effects, restricting its application to physicians trained in the treatment of anaphylaxis. This review discusses several new strategies to overcome these problems, which are presently a promising focus of research. These include the use of new adjuvants, of recombinant and genetically engineered venom allergens, as well as vaccination with peptides.

Are regulatory T cells the target of venom immunotherapy?

PURPOSE OF REVIEW

Allergen-specific immunotherapy is the only treatment that leads to lifelong tolerance to previously disease-causing allergens by restoring normal immunity against allergens. T-regulatory (TReg) cells are involved in preventing sensitization to allergens and represent a major target for venom- or other allergen-specific immunotherapy.

RECENT FINDINGS

Induction of peripheral tolerance in T cells, which is characterized mainly by suppressed proliferative and cytokine responses against the T-cell epitopes of major allergens, is an essential step in specific immunotherapy. It is initiated by the autocrine action of interleukin-10 and/or transforming growth factor-beta, which are produced by antigen-specific TReg cells. Tolerized T cells can be reactivated to produce distinct T-helper-1 or T-helper-2 cytokine patterns, thus directing allergen-specific immunotherapy toward successful or unsuccessful outcomes. TReg cells directly or indirectly influence effector cells of allergic inflammation, such as mast cells, basophils and eosinophils. In addition, there is accumulating evidence that they may suppress IgE production and induce IgG4 and IgA production against allergens. In addition, histamine released from mast cells and basophils may efficiently contribute to immunoregulation during specific immunotherapy, and affect TReg cells and the production of their cytokines via histamine receptor 2.

SUMMARY

By applying recent knowledge in TReg-cell-dependent mechanisms of peripheral tolerance, more rational and safer approaches to the prevention and cure of venom hypersensitivity may be developed in the future.

T regulatory cells in allergy: novel concepts in the pathogenesis, prevention, and treatment of allergic diseases

The identification of T regulatory (T(Reg)) cells as key regulators of immunologic processes in peripheral tolerance to allergens has opened an important era in the prevention and treatment of allergic diseases. Both naturally occurring CD4(+)CD25(+) T(Reg) cells and inducible populations of allergen-specific IL-10-secreting T(R)1 cells inhibit allergen-specific effector cells in experimental models. Allergen-specific T(Reg) cell responses contribute to the control of allergic inflammation in several ways. Skewing of allergen-specific effector T cells to a T(Reg) phenotype appears to be a crucial event in the development of a healthy immune response to allergens and successful outcome in allergen-specific immunotherapy. The increased levels of IL-10 and TGF-beta produced by T(Reg) cells can potently suppress IgE production while simultaneously increasing the production of the noninflammatory antibody isotypes IgG4 and IgA, respectively. T(Reg) cells directly or indirectly suppress effector cells of allergic inflammation, such as mast cells, basophils, and eosinophils, and contribute to remodeling in asthma and atopic dermatitis. In addition, mediators of allergic inflammation that trigger cyclic AMP-associated G protein-coupled receptors, such as histamine receptor 2, might play a role in peripheral tolerance mechanisms against allergens. Current strategies for drug development and allergen-specific immunotherapy exploit these observations with the potential to provide cure for allergic diseases.

BCG modulation of anaphylactic antibody response, airway inflammation and lung hyperreactivity in genetically selected mouse strains (Selection IV-A)

The effect of Bacillus Calmette-Guérin (BCG) treatment in allergic pulmonary reaction was studied in mice genetically selected accordingly to a High (H-IVA) or Low (L-IVA) antibody responsiveness. Mice were immunized with ovalbumin (OVA) or OVA plus BCG. Two days after nasal antigenic challenge, seric IgE and IgG1 anti-OVA, eosinophils in pulmonary tissue, inflammatory cells in bronchoalveolar lavage and the compliance and conductance of respiratory system were evaluated. H-IVA mice were found more susceptible than L-IVA, and BCG was able to inhibit simultaneously the production of IgE, the bronchopulmonary inflammation and bronchial hyperresponsiveness in these genetically selected mice.

CD4CD25 regulatory T lymphocytes in allergy and asthma

Allergic asthma is characterized by airway hyper-responsiveness and chronic mucosal inflammation mediated by CD4(+) Th2 lymphocytes. Regulatory CD4(+)CD25(+) T cells are important components of the homeostasis of the immune system, as impaired CD4(+)CD25(+) T cell activity can cause autoimmune diseases and allergy. The mechanism of suppression by CD4(+)CD25(+) T cells remains controversial; different in vivo and in vitro studies raise possible roles for the immunosuppressive cytokines interleukin-10 and transforming growth factor-beta, forkhead transcription factor Foxp3, glucocorticoid-induced tumor necrosis factor receptor, cytotoxic lymphocyte associated antigen-4, 4-1BB costimulator receptor, a CD4-related molecule LAG-3, and neuropilin-1. Current data suggest that Th2 responses to allergens are normally suppressed by CD4(+)CD25(+) T cells. Suppression by CD4(+)CD25(+) T cells is decreased in allergic individuals. Furthermore, CD4(+)CD25(+) T cells play a key role in regulating airway eosinophilic inflammation. The immunomodulatory properties of CD4(+)CD25(+) T cells do extend to Th2 responses, most notably by limiting the development of a proinflammatory CD4(+) Th2 phenotype characterized by reduced cytokine production. An understanding of the roles of CD4(+)CD25(+) T cells in vivo could provide better insight into the design of novel approaches to modulate the chronic airway inflammatory reaction evident in bronchial asthma.

Cytokines, allergy, and asthma

PURPOSE OF REVIEW

This review examines recent articles on the relationship of cytokines to allergy and asthma with particular emphasis on immune mechanisms involved in disease development in early life.

RECENT FINDINGS

It was previously proposed that reduced microbial exposure in early life is responsible for a shift of the Th1/Th2 balance in the immune system towards the proallergenic Th2 response. This Th1/Th2 imbalance results in the clinical expression of allergy and/or asthma. In recent years, accumulating data from mice and humans have identified Th2 cytokines [interleukin (IL)-4, IL-13, and IL-5] as major contributors to allergy and asthma. Interestingly, the Th1 cytokine interferon-gamma has recently been shown to act concurrently with Th2 cytokines in maintaining the chronic inflammatory response in allergic diseases, particularly in asthmatic airways. Most recently, evidence suggests that suppression of T-regulatory cells may contribute to the underlying immune mechanisms involved in allergy and asthma.

SUMMARY

An enhanced Th2 immune response and the elaboration of cytokines such as IL-4, IL-13, and IL-5 contribute to the induction of allergy and asthma. Interferon-gamma, a Th1 cytokine, acts in conjunction with Th2 (IL-4, IL-13, and IL-5) in maintaining chronic allergic inflammation. The mechanisms leading to an enhanced Th2 response are still controversial. Th2-dominated immune responses may result from immune suppression of T-regulatory cells as well as Th1 cells. Understanding early-life immune mechanisms responsible for atopic diseases, specifically how cytokines of T-regulatory cells act to balance the Th1 and Th2 immune response, continues to be a fruitful area of research.

T regulatory cells and allergy

Anergy, tolerance and active suppression may not be independent events, but rather involve similar mechanisms and cell types in immune regulation. Induction of allergen-specific T(Reg) cells seems essential for maintaining a healthy immune response towards allergens. By utilizing multiple secreted cytokines and surface molecules, antigen-specific T(Reg) cells may re-direct an inappropriate immune response against allergens or auto-antigens.