Allergen-specific T cells from birch-pollen-allergic patients and healthy controls differ in T helper 2 cytokine and in interleukin-10 production

Morphometric analysis of inflammation in bronchial biopsies following exposure to inhaled diesel exhaust and allergen challenge in atopic subjects

Background

Allergen exposure and air pollution are two risk factors for asthma development and airway inflammation that have been examined extensively in isolation. The impact of combined allergen and diesel exhaust exposure has received considerably less attention. Diesel exhaust (DE) is a major contributor to ambient particulate matter (PM) air pollution, which can act as an adjuvant to immune responses and augment allergic inflammation. We aimed to clarify whether DE increases allergen-induced inflammation and cellular immune response in the airways of atopic human subjects.

Methods

Twelve atopic subjects were exposed to DE 300 μg.m⁻³ or filtered air for 2 h in a blinded crossover study design with a four-week washout period between arms. One hour following either filtered air or DE exposure, subjects were exposed to allergen or saline (vehicle control) via segmental challenge. Forty-eight hours post-allergen or control exposure, bronchial biopsies were collected. The study design generated 4 different conditions: filtered air + saline (FAS), DE + saline (DES), filtered air + allergen (FAA) and DE + allergen (DEA). Biopsies sections were immunostained for tryptase, eosinophil cationic protein (ECP), neutrophil elastase (NE), CD138, CD4 and interleukin (IL)-4. The percent positivity of positive cells were quantified in the bronchial submucosa.

Results

The percent positivity for tryptase expression and ECP expression remained unchanged in the bronchial submucosa in all conditions. CD4 % positive staining in DEA (0.311 ± 0.060) was elevated relative to FAS (0.087 ± 0.018; p = 0.035). IL-4 % positive staining in DEA (0.548 ± 0.143) was elevated relative to FAS (0.127 ± 0.062; p = 0.034). CD138 % positive staining in DEA (0.120 ± 0.031) was elevated relative to FAS (0.017 ± 0.006; p = 0.015), DES (0.044 ± 0.024; p = 0.040), and FAA (0.044 ± 0.008; p = 0.037). CD138 % positive staining in FAA (0.044 ± 0.008) was elevated relative to FAS (0.017 ± 0.006; p = 0.049). NE percent positive staining in DEA (0.224 ± 0.047) was elevated relative to FAS (0.045 ± 0.014; p = 0.031).

Conclusions

In vivo allergen and DE co-exposure results in elevated CD4, IL-4, CD138 and NE in the respiratory submucosa of atopic subjects, while eosinophils and mast cells are not changed.

Trial registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01792232.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0114-z) contains supplementary material, which is available to authorized users.

Interplay of air pollution and asthma immunopathogenesis: a focused review of diesel exhaust and ozone

Controlled human exposure experiments with diesel exhaust particles (DEPs) and ozone serve to illustrate the important role pollutants play in modulating both allergic mechanisms and immune responses to affect the immunopathogenesis of airway diseases such as asthma. For DEP, evidence is stronger for the exacerbation of existing asthma rather than for the development of new disease. To the extent that this enhancement occurs, the augmentation of Th2-type immunity seems to be a common element. For ozone, neutrophilic inflammation, altered immune cell phenotype and function and oxidative stress are all marked responses that likely contribute to underlying immune-inflammatory features of asthma. Evidence is also emerging that unique gene signatures and epigenetic control of immune and inflammatory-based genes are playing important roles in the magnitude of the impact ozone is having on respiratory health. Indeed, the interplay between air pollutants such as DEP and ozone and asthma immunopathogenesis is an ongoing concern in terms of understanding how exposure to these agents can lead to worsening of disease. To this end, asthmatics may be pre-disposed to the deleterious effects of pollutants like ozone, having constitutively modified host defense functions and gene signatures. Although this review has utilized DEP and ozone as example pollutants, more research is needed to better understand the interplay between air pollution in general and asthma immumopathogenesis.

Mechanisms of peripheral tolerance to allergens

The immune system is regulated to protect the host from exaggerated stimulatory signals establishing a state of tolerance in healthy individuals. The disequilibrium in immune regulatory vs effector mechanisms results in allergic or autoimmune disorders in genetically predisposed subjects under certain environmental conditions. As demonstrated in allergen-specific immunotherapy and in the healthy immune response to high-dose allergen exposure models in humans, T regulatory cells are essential in the suppression of Th2-mediated inflammation, maintenance of immune tolerance, induction of the two suppressive cytokines interleukin-10 and transforming growth factor-β, inhibition of allergen-specific IgE, and enhancement of IgG4 and IgA. Also, suppression of dendritic cells, mast cells, and eosinophils contributes to the construction of peripheral tolerance to allergens. This review focuses on mechanisms of peripheral tolerance to allergens with special emphasis on recent developments in the area of immune regulation.

Immune responses to inhalant allergens

This overview describes the nature of the immune responses induced by the inhalation of allergens. There is a dichotomy in that B cells have multiple mechanisms that limit the amount of immunoglobulin E (IgE) antibody production, whereas T-cell responses are large even in nonallergic subjects. With the possible exception of responses to cat allergen, however, T cells from nonallergic subjects have limited effector function of helping IgG antibody, and in house-dust mite allergy, this declines with age. Regulation by interleukin 10 (IL-10)-producing cells and CD25⁺ T-regulatory cells has been proposed, but critically, there is limited evidence for this, and many studies show the highest IL-10 production by cells from allergic subjects. Recent studies have shown the importance of nonlymphoid chemokines thymic stromal lymphopoietin and IL-27, so studying responses in situ is critical. Most sources of allergens have 1 or 2 dominant allergens, and for house-dust mite, it has been shown that people have a predictable responsiveness to high-, mid-and poor-IgE-binding proteins regardless of the total size of their response. This allergen hierarchy can be used to design improved allergen preparations and to investigate how antiallergen responses are regulated.

Effect of Pru p 3 on dendritic cell maturation and T-lymphocyte proliferation in peach allergic patients

BACKGROUND

Pru p 3 is the major peach allergen and the most frequent cause of food allergy in adults in the Mediterranean area. Although its allergenicity is well characterized, its ability to generate a T-cell response is not completely known.

OBJECTIVE

To investigate the influence of Pru p 3 allergen on dendritic cell (DC) maturation and specific T-cell response (T(H)1/T(H)2) in peach allergic patients.

METHODS

Peach allergic patients (n = 11) and tolerant controls (n = 14) were included in the study. Monocyte-derived DC maturation after incubation with Pru p 3 was evaluated by the increase of maturational markers (CD80, CD86, and CD83) by flow cytometry. Lymphocyte proliferation was evaluated by coculturing monocyte-derived DCs and 5,6-carboxyfluorescein diacetate N-succinimidyl ester-stained lymphocytes with different concentrations of Pru p 3 (25, 10, and 1 μg/mL) by flow cytometry and cytokine production.

RESULTS

Pru p 3 induced a significant increase in the CD80, CD86, and CD83 expression on stimulated DCs from patients compared with controls. The lymphocyte proliferative response after Pru p 3 stimulation was also significantly higher along with an increase in interleukin 8 in patients compared with tolerant controls.

CONCLUSION

Pru p 3 allergen induces changes in DC maturational status mainly in peach allergic patients. An increase in lymphocyte proliferative response accompanied with a different cytokine pattern was also observed compared with healthy controls.

Allergen-specific T cell quantity in blood is higher in allergic compared to nonallergic individuals

Background

Allergen-specific IgE production is a hallmark of allergic asthma/rhinitis/eczema. Theoretically this could be due to a high number of allergen-specific B cells or allergen-specific T cells helping allergen-specific B cells differentiate into IgE-producing plasma cells. Here, we determined whether the number of allergen-specific B cells or T helper (Th) cells is higher in allergic individuals compared to nonallergic individuals.

Methods

A total of 52 allergic individuals and 32 nonallergic individuals were studied. The allergen-specific B and Th cells were enumerated by culturing CFSE-loaded blood mononuclear cells for 7-days with allergen (cat, Timothy or birch), and determining the number of proliferating B or Th cells (diluting CFSE) by flow cytometry. Allergen-specific IgE concentration was determined by fluorescent enzymoimmunoassay (FEIA).

Results

The quantities of proliferating Th cells but not proliferating B cells specific for cat, Timothy and birch were significantly higher in cat-, Timothy- and birch-allergic individuals compared to nonallergic individuals. The titer of allergen-specific IgE showed significant correlation with allergen-specific Th cells and not with allergen-specific B cells for all 3 allergens.

Conclusions

A high number of allergen-specific proliferating Th cells, but not proliferating B cells, may play a role in the pathogenesis of allergic asthma/rhinitis/eczema.

Bet v 1 and its homologous food allergen Api g 1 stimulate dendritic cells from birch pollen-allergic individuals to induce different Th-cell polarization

BACKGROUND

Bet v 1 is the most relevant sensitizing protein for birch pollen (BP)-allergic individuals. Its homologues from plant foods are mainly involved in allergic reactions caused by IgE cross reactivity. We aimed to evaluate the polarizing effect of dendritic cells (DCs) pulsed with Bet v 1, Mal d 1, Api g 1 or Dau c 1 on Th-cell responses.

METHODS

Immature DCs were generated from peripheral blood monocytes of BP-allergic and healthy donors by culture with GM-CSF and IL-4 and subsequently pulsed with allergens in combination with maturation factors. Cell surface markers were analysed by FACS. Mature DCs were co-cultured with autologous Th cells and T-cell proliferation and cytokine profiles were determined.

RESULTS

In co-culture, mature allergen-pulsed DCs induced autologous Th cells of BP-allergic donors to proliferate significantly more than those of healthy individuals. Exposure of DCs from BP-allergic donors to Bet v 1 resulted in a robust Th2 skewing with significantly higher quantities of IL-5 and elevated IL-13 compared to maturation factors. In contrast, Api g 1-primed DCs from BP allergics significantly enhanced the production of the Th1 cytokine IFN-γ and significantly down-regulated IL-13 compared to maturation factors. In healthy donors, no significant cytokine production could be detected.

CONCLUSION

Bet v 1 in contrast to homologous food allergens seems to possess distinct molecular features that enable it to condition DCs from BP-allergic donors to induce allergen-specific T-cell proliferation and Th2 polarization.

Dynamics in cytokine responses during the development of occupational sensitization to rats

BACKGROUND

Occupational allergy forms an attractive model to study the development of allergic responses, as in some occupations it has a high incidence and develops quickly. In a cohort of starting laboratory animal workers, we previously found 20% sensitization to animal allergens within 2 years.

METHODS

We compared cellular responses of incident laboratory animal workers who developed rat-specific sensitization (cases, n = 18) during 2 years of follow-up to control animal workers matched for atopic status but without sensitization after follow-up (controls, n = 18). Practically, this is a case-control study, nested within the cohort. Rat-specific IgE antibodies were measured in sera, and allergen-specific and nonspecific cytokine responses were measured in whole blood and in isolated peripheral blood mononuclear cells.

RESULTS

Self-reported allergic symptoms were related to the presence of rat-specific IgE (P ≤ 0.01). Cases developed a rat allergen-specific interleukin (IL)-4 response during sensitization, while controls did not show an increased IL-4 response (at visit D: 33 vs 5 IL-4 producing cells/10(6) cells, P < 0.001). The IL-4 response was related to the levels of rat-specific IgE in cases (visit D: rho = 0.706, P < 0.001). By contrast, allergen-specific IL-10 and interferon γ (IFNγ) responses as well as nonspecific cytokine responses were comparable between cases and controls.

CONCLUSION

This study is the first to show the development of an allergen-specific IL-4 response in adult human subjects during allergen-specific sensitization. This IL-4 response was quantitatively associated with the development of the specific IgE antibodies. Allergen-specific or nonspecific IL-10 and IFNγ responses showed no protective effect on the development of allergic sensitization.

Allergen provocation increases TH2-cytokines and FOXP3 expression in the asthmatic lung

BACKGROUND

Allergic asthma is caused by allergen-specific IgE and T-helper cell (Th) type 2 responses towards airborne allergens. The objective of this study was to investigate local and systemic regulatory mechanisms in the early asthmatic response to bronchial allergen provocation.

METHODS

Birch pollen-allergic patients with mild asthma (n = 13) and healthy nonallergic controls (n = 14) were subjected to bronchoalveolar lavage (BAL) and blood sampling. On patients BAL was performed twice: without preceding provocation ('before samples') and 24 h after bronchial provocation with birch pollen allergen. Lymphocytes in BAL and peripheral blood mononuclear cells (PBMCs) were phenotyped by multi-colour flow cytometry and cytokines measured by cytometric bead array. Proliferation and secreted cytokines were analysed in allergen-stimulated PBMCs, CD25(+) depleted PBMCs and PBMCs with IL-10 neutralizing antibodies.

RESULTS

The numbers of CD69(+) and FOXP3(+) lymphocytes were higher in BAL after compared with before allergen provocation in asthmatic patients. Moreover, allergen provocation increased expression of FOXP3 in CD4(+)CD25(bright) cells. The cytokine profile in BAL fluid from asthmatics revealed higher levels of IL-5, compared with the controls, and an increase in IL-5, IL-6, IL-9 and IL-10 after allergen provocation. Pollen allergen stimulated PBMC cultures from asthmatic patients produced elevated levels of IL-5 and IL-13 compared with the controls, which were not affected by depletion of CD25(+) cells or IL-10 neutralization.

CONCLUSION

Despite an increase in CD4(+)CD25(bright) cells expressing high levels of FOXP3 in response to bronchial allergen provocation, asthmatic patients exhibit enhanced levels of Th2 cytokines in the lung, which may indicate an inability among infiltrating cells to suppress Th2 responses.

T helper 2 biased de novo immune response to Keyhole Limpet Hemocyanin in humans

BACKGROUND

Allergen-specific T helper 2 (Th2) cells play an important role in the pathogenesis of atopic disorders. To date, no model system exists in humans that would allow the monitoring of a developing de novo Th2 immune response in vivo.

OBJECTIVE

The aim of the experiment was to establish an immunization protocol inducing a de novo Th2 response in humans using Keyhole Limpet Hemocyanin (KLH) as neo-antigen.

METHODS

The double-blind placebo-controlled, parallel-group study was conducted in two groups of subjects (16 healthy volunteers and 16 patients with allergic rhinitis). Subjects received three i.m. injections of 100 microg KLH adsorbed to aluminium hydroxide or matching placebo (alum alone) in intervals of 2 weeks. On day 43, KLH alone (10 microg) was given intra-dermally (i.d.) to all subjects to assess immediate and late-phase skin responses.

RESULTS

The immunization protocol was well tolerated, highly specific and efficient. Antigen-specific production of Th2-cytokines (mainly IL-5 and IL-13) by PBMCs suggested a Th2 pattern, as did the presence of KLH-specific IgG4 in sera. Intra-dermal KLH challenge induced an immediate-type of response predominantly in atopic subjects followed by a late-phase skin reaction. The latter was accompanied by the presence of IgE(+) cells, eosinophils and a strong up-regulation of IL-4 and IL-13 along with the absence of Th1 transcripts in biopsies taken from the site of antigen challenge. IL-17 and IL-22 transcripts were detected only in healthy subjects skin following KLH challenge, while IL-1beta and IL-33 expression did not differ between the healthy and the atopics.

CONCLUSIONS

The immunization protocol resulted in the elicitation of a local and peripheral Th2 immune response in both healthy and atopic individuals. This may permit the investigation and monitoring of novel immunomodulatory strategies aiming to interfere with Th2 responses in man. The relevance of lack of Th17 cells in atopic skin in this model remains to be determined.

The major horse allergen Equ c 1 contains one immunodominant region of T cell epitopes

BACKGROUND

Despite the fact that most significant mammalian respiratory allergens are lipocalin proteins, information on the human T cell reactivity to these allergenic proteins is largely missing.

OBJECTIVE

Knowing the T cell epitopes in allergens is a prerequisite for developing novel preparations for allergen immunotherapy.

METHODS

Specific T cell lines were generated with recombinant Equ c 1 from the peripheral blood mononuclear cells (PBMCs) of 10 horse-allergic subjects. For determining T cell epitopes, the lines were stimulated with 16mer synthetic Equ c 1 peptides overlapping by 14 amino acids. The binding capacity of Equ c 1 peptides to human leucocyte antigen class II molecules was determined by the competitive ELISA.

RESULTS

The major horse allergen Equ c 1 resembles two other lipocalin allergens, the major cow allergen Bos d 2 and the major dog allergen Can f 1, in that it is weakly stimulatory for the PBMCs of sensitized subjects. Moreover, the T cell epitopes of Equ c 1 are clustered in a few regions along the molecule, as is the case with Bos d 2 and Can f 1. Similar to Bos d 2, Equ c 1 contains one immunodominant epitope region at the carboxy-terminal end of the molecule. The T cell lines of eight horse-allergic subjects out of 10 showed strong reactivity to one or both of the two overlapping peptides, p143-158 and p145-160, in this region. The region probably contains two overlapping epitopes.

CONCLUSION

The 18mer peptide p143-160 from the immunodominant region of Equ c 1 is a potential candidate for the peptide-based immunotherapy of horse-sensitized subjects.

Impaired Maturation of Monocyte-derived Dendritic Cells from Birch Allergic Individuals in Association with Birch-specific Immune Responses

Optimal activation of T lymphocytes requires a costimulatory signal provided by the interaction of molecules on the surface of T cells with their ligands expressed on dendritic cells (DC). We investigated whether DC differentiated from monocytes from healthy and birch allergic asthmatic individuals and further maturated by stimulation with cat and birch allergens and LPS differ in their phenotypic receptor expression. Similar expression of DC surface markers, including HLA-DR, CD80, CD86, CD83, CD1a and CD11c, was detected in monocyte-derived DC from allergic and healthy individuals. Cells from healthy donors stimulated either antigen showed a similar activation of the CD80 and double CD80/CD86 costimulatory molecules when compared with non-stimulated cells. In the case of cells from allergic individuals, birch allergen was unable to produce the same increased expression of CD80 alone or in combination with CD80/CD86, in comparison with cells stimulated with cat and LPS. Levels of IL-6, IL-8, IL-10, MCP-1/MCAF and MIP-1beta were similar in the supernatant of non-stimulated DC from both groups of subjects. By contrast, the spontaneous secretion of IL-12p70 and TNF-alpha was higher in the supernatant of DC from healthy subjects when compared with that from allergic individuals. Stimulation with birch and LPS resulted in an increased secretion of IL-12p70 in samples from healthy when compared with that in allergic individuals. The results suggest an impaired specific maturation of DC from birch allergic individuals in association with birch-specific immune responses. Lower secretion of IL-12p70 from birch-stimulated DC from allergic individuals suggests that not only maturation, but also the specific Th1 function of these cells seems to be affected in those individuals.

Immunomodulatory constituents of human milk change in response to infant bronchiolitis

Although epidemiological evidence is generally supportive of a causal association between respiratory syncytial virus (RSV) bronchiolitis during infancy and the development of persistent wheeze/asthma, if not allergy, the mechanism by which this occurs and an explanation for why all children do not succumb remains to be elucidated. Breast feeding has been found to confer a protective effect against respiratory infections such as RSV bronchiolitis and allergy; however, again there is little direct evidence and no clear mechanism. In this study, we examined whether human milk immunomodulatory factors (cells, cytokines) change in response to clinically diagnosed, severe bronchiolitis in the recipient breast-fed infant. We examined milk from 36 breast feeding mothers of infants hospitalized with bronchiolitis and compared them with milk from 63 mothers of postpartum age-matched healthy controls. Milks from mothers of infants hospitalized with bronchiolitis had significantly greater numbers of viable cells when compared with the milks obtained from mothers of healthy infants (1.3 +/- 0.4 vs. 0.3 +/- 0.03 x 10(6) cells/ml, mean +/- s.e.m.; p < or = 0.001). Further, the cells obtained from the mothers of infants hospitalized with bronchiolitis were found to produce a skewed cytokine profile ex vivo in response to stimulation by live RSV but not when cultured with a non-specific mitogen (concanavalin A). This study provides preliminary evidence for an immunological link between mothers and their breast-fed infants during severe respiratory infections as well as a possible contributing factor to the development of persistent wheeze in these infants.

Intracellular production of IL-2, IL-4, IFN-gamma, and TNF-alpha by peripheral blood CD3+ and CD4+ T cells in children with atopic dermatitis

The role of the type-2 T helper (Th2) cell-mediated immune response in the immunopathogenesis of atopic dermatitis (AD) is well documented. Whether polarized immunoresponse is confined to antigen-specific T cells or is distributed among all T cell subsets is still controversial. We investigated frequencies of interleukin-2 (IL-2), IL-4, interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha) producing CD3(+) and CD4(+) T cells in peripheral blood from children with atopic dermatitis and healthy subjects with and without in vitro stimulation. Children with severe AD had a significantly lower percentage of CD4(+) T cells spontaneously expressing IL-4 compared with healthy controls (p <0.01). Polyclonal stimulation significantly increased cytokine production in both AD patients and healthy individuals. Frequencies of CD3(+) and CD4(+) producing IL-2, IL-4, IFN-gamma, and TNF-alpha after in vitro stimulation with phorbol-12-myristate 13-acetate (PMA) + ionomycin were comparable in the AD and control groups. In response to PMA/ionomycin, children with AD and asthma symptoms had a significantly lower percentage of CD3(+) T cells producing TNF-alpha. We failed to demonstrate evidence of an imbalance with respect to type-2 cytokine productions in children with AD. Comparable induction of Th1 and Th2 cytokines in polyclonally stimulated peripheral CD3(+) and CD4(+)T cells from AD patients and controls puts into question the polarized Th2 immune response as a general characteristic of T cells in children with atopic dermatitis.

Novel therapeutic interventions for allergic rhinitis

Allergic rhinitis is a high-prevalence disease, affecting 10 - 20% of the general population. Allergic rhinitis is sustained by an IgE-mediated reaction and by a complex inflammatory network of cells, mediators and cytokines that becomes chronic when exposure to allergen persists. A T(H)2-biased immune response is the background of the allergic inflammation. The current therapeutic strategy is mainly based on drugs (antihistamines, nasal corticosteroids, cromones and decongestants) and allergen immunotherapy. Drugs are (overall) effective in controlling symptoms but do not modify the immune background that leads to allergic inflammation and safety concerns may be present, especially for prolonged treatments. Immunotherapy can modify the allergic response but there is still room for improvement. Nowadays, several approaches are under investigation to optimise the management of allergic rhinitis. On one hand, new drugs and antimediators are being developed. On the other hand, attempts are being made to selectively block relevant signal pathways of allergic reaction. Finally, one of the major goals is to modify the T(H)2-biased immune response by improving the characteristics and modes of action of allergen immunotherapy.

Immunological characteristics of subjects with asymptomatic skin sensitization to birch and grass pollen

BACKGROUND

Asymptomatic skin sensitization (AS) has been shown to be a risk factor for respiratory allergic disease.

OBJECTIVE

We investigated allergen and recall antigen-driven T cell proliferation, cytokine production and T cell expression of the chemokine receptor CCR4, in cultures derived from symptomatic atopics (SA), subjects with AS and healthy controls (HC). Numbers of allergen-specific precursor T cells in all three groups were also estimated.

METHODS

Peripheral blood mononuclear cells from the three groups were isolated and stimulated with allergen and tetanus toxoid. Proliferation, cytokine production and CCR4 expression were measured by flow cytometry.

RESULTS

A significantly increased proportion of CD4(+) memory T cells proliferated in response to allergen in SA as compared with subjects with AS (P<0.001) and HC (P<0.001). Only in SA was expansion of CD4(+)CCR4(+) T cells, after allergen stimulation observed. SA had higher frequencies of allergen-specific T cells than subjects with AS and HC (P=0.02, for both). With regard to allergen-induced production of T-helper type 1 (Th1) and Th2 cytokines, subjects with AS and HC resembled each other, while differing significantly from SA.

CONCLUSION

We conclude, that subjects with AS, although clearly IgE sensitized, have significant diminished numbers of allergen-specific T cells as well as decreased allergen-induced CD4(+) memory T cell proliferation as compared with SA. To a large extent, our findings are capable of explaining the immunological characteristics associated with AS. Our findings may serve as better prognostic markers for subsequent allergic progression, than previously described clinical and paraclinical characteristics.

Emerging anti-inflammatory agents for allergic rhinitis

Allergic rhinitis (AR) is a high-prevalence disease, affecting 10-15% of the general population. AR is sustained by an IgE-mediated reaction, and by a complex inflammatory network of cells, mediators and cytokines that becomes chronic when exposure to allergen persists. A T helper 2 (TH2)-biased immune response is the basis for the allergic inflammation. The current therapeutic strategy is mainly based on drugs (antihistamines, nasal corticosteroids, cromones, decongestants) and allergen immunotherapy. Drugs are overall effective in controlling symptoms, but do not modify the immune background that leads to allergic inflammation, and safety concerns may be present especially for prolonged treatments. Immunotherapy can modify the allergic response, but there is still space for improvement. Nowadays, several approaches are under investigation to optimise the management of AR. On one hand, new drugs and antimediators are being developed; on the other hand, attempts are made to selectively block relevant signal pathways of allergic reaction. Finally, one of the major goals is to modify the TH2-biased immune response by improving the characteristics and modes of action of allergen immunotherapy.

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.

House dust mite-specific T cells in healthy non-atopic children

BACKGROUND

T-helper type 2 (Th2) cells play an important role in the pathogenesis of allergic diseases. Recent studies have demonstrated that allergen-specific T cells can also be found in the blood of healthy individuals. Both IL-10 and IFN-gamma might modulate the induction and maintenance of allergen-specific tolerance.

AIM

To study the phenotype and functional characteristics of allergen-specific T cells in healthy non-atopic children.

METHODS

Peripheral blood mononuclear cells (PBMC) from 13 symptomatic house dust mite (HDM)-allergic children and from nine matched healthy control children were stimulated with recombinant (r)Der p 2, a major allergen from HDMs.

RESULTS

Stimulation with rDer p 2 resulted in Th2 cytokine production in cultures of PBMC from allergic but not from healthy children. In contrast, IL-10 and IFN-gamma were induced in PBMC cultures from both healthy and HDM-allergic children. Intracellular staining revealed that IL-10 and IFN-gamma are largely produced by the same T cells. Stimulation of T cells from healthy children with rDer p 2 also induced expression of inducible costimulator (ICOS) on a small T cell subset.

CONCLUSION

Allergen-specific memory T cells from healthy non-atopic children produce IL-10 and IFN-gamma (but not Th2 cytokines) and express ICOS upon stimulation. These cells might be responsible for a normal immune balance after allergen encounter in non-atopics.

Induction of interleukin 10 by sublingual immunotherapy for house dust mites: a preliminary report

BACKGROUND

Subcutaneous specific immunotherapy has been demonstrated to be capable of inducing T-cell regulatory response. Interleukin 10 (IL-10) plays a crucial role in inducing allergen-specific tolerance; however, no previous studies have examined IL-10 production after sublingual immunotherapy (SLIT).

OBJECTIVE

To evaluate T-cell proliferation and IL-10 production in patients successfully treated with SLIT for house dust mites (HDMs).

METHODS

Peripheral blood mononuclear cells were isolated from patients after at least 3 years of successful HDM SLIT and from matched untreated allergic patients and healthy control subjects. After 3 and 6 days of in vitro stimulation with phytohemagglutinin (PHA), Candida albicans, and Dermatophagoides farinae, proliferation and production of IL-10 were measured.

RESULTS

Patients treated with SLIT showed a significant reduction of proliferation induced by C albicans compared with untreated atopic patients (P < .001), but a significant reduction was also demonstrated in healthy controls compared with untreated atopic patients (P < .001). Patients treated with SLIT also showed a significant increase of IL-10 production after Candida and PHA stimuli compared with patients with untreated rhinitis (P < .001 for both). Patients with untreated rhinitis did not produce IL-10.

CONCLUSION

This preliminary study confirms reduced T-cell proliferation and preliminarily provides the first evidence, to our knowledge, of peripheral IL-10 production in allergic patients successfully treated with HDM SLIT.

The effect of treatment with montelukast on in vitro interleukin-10 production of mononuclear cells of children with asthma

BACKGROUND

The effects of leukotriene modifiers on IL-10 production have not been studied in children with asthma.

OBJECTIVE

The primary objective of this study was to determine the changes in IL-10 concentrations, clinical efficacy and peripheral blood eosinophil counts after treatment with montelukast.

METHODS

The study was conducted on 27 patients: 13 patients monoallergic to grass pollen during the pollen season (GPs group) and out of the pollen season (GPos group), and on 14 patients monoallergic to house dust mite (HDM) from May to September (HDM group). Main outcome measures were changes in concentrations of IL-10 in the supernatant after a 4-week treatment with montelukast. Measurements of asthma severity score, forced expiratory volume in 1 s (FEV1) and peripheral blood eosinophil counts were the secondary end-points.

RESULTS

Montelukast resulted in a within-group significant increase in IL-10 concentration in the supernatant in the GPs (54.0 vs. 125.5 pg/mL) and in the HDM (51.2 vs. 77.1 pg/mL) group. Montelukast had no effect on changes of IL-10 concentration in the supernatant from peripheral blood mononuclear cell (PBMC) culture after non-sensitizing allergen stimulation. Montelukast significantly improved asthma control and FEV1, and significantly decreased eosinophil blood count in the GPs and in the HDM group after a 4-week treatment. Montelukast did not lead to changes of all measured parameters within the GPos group.

CONCLUSION

Montelukast increased IL-10 concentration in supernatants from sensitizing allergen-stimulated PBMC culture obtained from children with asthma monoallergic to grass pollen during the pollen season, and from children with asthma monoallergic to HDM.