A Role for IL-10-Mediated HLA-DR7-Restricted T Cell-Dependent Events in Development of the Modified Th2 Response to Cat Allergen

Analysis of T-helper responses and FOXP3 gene expression in patients with Japanese cedar pollinosis

BACKGROUND

Evidence has been accumulated indicating that regulatory T (T-reg) cells play a crucial role in the maintenance of peripheral T-cell tolerance to allergens. To explore the role of FOXP3, which is required for the development of T-reg cells, in allergen-specific immune responses, we examined the relationship between the alteration of FOXP3 gene expression and in vitro immune responses against allergens.

METHODS

Peripheral blood mononuclear cells obtained from 19 human histocompatibility leukocyte antigens (HLA)-DPB1*0501 donors, including patients with Japanese cedar pollinosis and nonallergic healthy donors, were stimulated with Cry j 1 p61-75 peptide. On day 7, T cells were tested for peptide-specific reactivity in IFN-gamma and interleukin (IL)-5 enzyme-linked immunospot (ELISPOT) assays. Real-time quantitative RT-PCR was performed to assess relative change of FOXP3 gene expression before and after in vitro stimulation. Neutralization assays using anti-glucocorticoid-induced tumor necrosis factor receptor family-related protein (GITR) and anti-IL-10 monoclonal antibody were also performed.

RESULTS

Of 14 patients with allergic pollinosis tested, 10 responders displayed T-helper type 2 (Th2)-polarized reactivity to Cry j 1 p61-75, and 2 donors showed Th0 responses. Notably, the change of FOXP3 gene expression in donors showing peptide-specific T-helper responses was significantly lower than that in nonresponders, regardless of allergic pollinosis.

CONCLUSION

Our data indicate that FOXP3 is functional in nonallergic healthy donors as well as allergic patients, and FOXP3-expressing T cells may be responsible for the down-regulation of allergen-specific T-helper responses in individuals. A better understanding of the nature and specificity of FOXP3-expressing T cells in a suppressive mechanism is necessary to develop new immunotherapies against allergic rhinitis.

The role of infection in asthma

This paper reviews the impact of infections on the onset and clinical course of bronchial asthma. A just emphasis is given to the role viral infections, particularly rhinovirus infections, play in exacerbations, and that played by respiratory syncytial virus, suspected of triggering the asthmatic syndrome. The mechanisms of the immune response to virus attacks are explained, highlighting the asthmatic and allergic patient's weakened response, particularly in the perinatal period. Further stressed is a potentiating effect of viral aggression on the allergic response. The hygiene hypothesis and its lack of scientific consistency is detailed, at least as far as the role it seeks to confer on an unproven antagonism of the Th1 and Th2 lymphocyte responses. The current importance of research not into bacteria, but into bacterial products, including endotoxins, on the modulation of asthma and allergy is noted. Studies which, along these lines, show an environmental impact on genetic secretion in the phenotype are underlined. Also discussed in passing are several mechanisms which go towards explaining neutrophilic asthma - for many a contradiction, given eosinophilia's stranglehold on asthmatic inflammation.

Infecção na modulaçâo da asma11Trabalho apresentado no XXIII Congresso de Pneumologia da SPP – Guarda, Novembro 2007 / Paper presented at the XXIII Congresso de Pneumologia da SPP / PSP Pulmonology Congress, Guarda, November 2007

Faz-se uma revisão da influência das infecções no aparecimento e na clínica da asma brônquica. Dá-se o relevo que merece à intervenção virusal, sobretudo ao rinovírus, pela sua influência nas exacerbações, e ao vírus sincicial respiratório, sobre o qual recai a suspeita de poder ser causa determinante no aparecimento da síndroma asmática. Tentam-se esclarecer os mecanismos da resposta imune à agressão virusal em função das debilidades da resposta do asmático e do atópico, sobretudo no período perinatal, salientando-se, ainda, um efeito de potenciação da agressão virusal sobre a resposta atópica. Aborda-se a hipótese higiénica e a sua falta de consistência científica, pelo menos no papel que pretende atribuir a um não demonstrado antagonismo das respostas linfocitárias Th₁ e Th_2, apontando-se a importância actual da investigação, não das bactérias mas dos produtos bacterianos, como as endotoxinas, na modulação da asma e da atopia, dando-se relevo aos estudos que, a partir deste modelo, demonstram uma influência do ambiente na secreção génica e, consequentemente, no fenótipo. Invocam-se, nas entrelinhas, vários mecanismos que podem explicar a asma neutrofílica que, para muitos, é um paradoxo perante o consagrado domínio do eosinófilo na inflamação asmática.

Rev Port Pneumol 2008; XIV (5): 647-675

Cholera toxin B subunit promotes the induction of regulatory T cells by preventing human dendritic cell maturation

Cholera toxin B subunit (CTB) is an efficient mucosal carrier molecule for the generation of immune responses to linked antigens. There is also good evidence that CTB acts as an immunosuppressant, as it is able to down-modulate human monocyte/macrophage cell line activation and to suppress Th1-type responses. In the present study, we examined the possibility that recombinant CTB (rCTB) may affect human dendritic cell (DC) functions in response to LPS stimulation and may induce the generation of DC with the capacity to generate CD4(+) regulatory T cells (Tregs). Our findings show that rCTB partially prevents the LPS-induced maturation process of monocyte-derived DC (MDDC) and decreases their IL-12 production with no relevant effect on IL-10 production. LPS-stimulated MDDC pretreated with rCTB are able to promote the induction of low proliferating T cells, which show an enhanced IL-10 production associated with a reduced IFN-gamma production and the same high levels of TGF-beta as the control. These T cells suppress proliferation of activated autologous T cells. Transwell experiments and blockade of IL-10R and TGF-beta showed that the immunomodulatory effect is mediated by soluble factors. Thus, T cells induced by rCTB-conditioned MDDC acquire a regulatory phenotype and activity similar to those described for type 1 Tregs.

Cat ownership is a risk factor for the development of anti-cat IgE but not current wheeze at age 5 years in an inner-city cohort

BACKGROUND

Cat ownership is inversely associated with atopy and asthma in some areas of the world, but the relevance of cat ownership to allergic disease in the inner city is less known.

OBJECTIVE

We sought to evaluate the relationship between cat ownership and the development of early sensitization and wheeze.

METHODS

By using a prospective birth cohort study, Dominican and African American mothers living in New York City underwent repeated questionnaires about their child from birth to age 5 years. Sera collected from children at ages 2 (n = 323), 3 (n = 336), and 5 (n = 242) years were assayed for anti-cat IgE and anti-Fel d 1 IgG antibodies.

RESULTS

Cat ownership was a significant risk factor for the development of anti-cat IgE by age 2 years (risk ratio [RR], 6.4; 95% CI, 1.9-22) but not for anti-cat IgE development between the ages of 2 and 5 years (RR, 0.88; 95% CI, 0.24-2.3). Current wheeze was significantly more common among those children with anti-cat IgE at ages 3 (RR, 3.5; 95% CI, 2.1-6.0) and 5 (RR, 3.4; 95% CI, 2.3-4.9) years. Cat ownership was inversely associated with current wheeze at age 5 years among children without anti-cat IgE (RR, 0.26; 95% CI, 0.083-0.81). Among children with anti-cat IgE, a similar trend was observed (RR, 0.57; P = .044, Fisher exact test), although one with borderline statistical significance.

CONCLUSIONS

Despite a positive association with sensitization, cat ownership in this inner-city cohort was inversely associated with wheeze, potentially suggesting an IgE-independent protective mechanism in this community.

Targeting Fel d 1 to FcgammaRI induces a novel variation of the T(H)2 response in subjects with cat allergy

BACKGROUND

Induction of CD4+ T cells that produce IL-10 or IFN-gamma is central to the protective effects of conventional allergen immunotherapy.

OBJECTIVE

We examined the T-cell modulatory capacity of a fusion protein (H22-Fel d 1) that targets Fel d 1 to the high-affinity IgG receptor (FcgammaRI) on antigen-presenting cells.

METHODS

Monocyte-derived dendritic cells pulsed with H22-Fel d 1 were analyzed for surface phenotype and cytokine secretion by flow cytometry and cytometric bead assay, respectively. CD4+ T cells generated after coculture with H22-Fel d 1-pulsed dendritic cells were analyzed at the single-cell level by flow cytometry after intracellular cytokine staining. The T-cell repertoire was compared for subjects with (IgE+) and without cat allergy (IgE(neg)IgG(neg)), including subjects with a modified T(H)2 response (IgE(neg)IgG+).

RESULTS

H22-Fel d 1 induced a semimature phenotype in dendritic cells in conjunction with a selective increase in IL-5+ and IL-10+ CD4+ T cells compared with nonreceptor-targeted Fel d 1. Amplified T cells included diverse subtypes characteristic of T(H)0 (IL-5+IFN-gamma+), regulatory T(H)1 (IL-10+IFN-gamma+) and regulatory T(H)2 (IL-10+IL-5+ cells. T-cell qualitative changes were restricted to subjects with allergy and were distinct from a modified T(H)2 response. Blocking IL-10 induced by H22-Fel d 1 selectively increased IL-5+ CD4+ T cells, suggesting that T(H)2 responses were controlled.

CONCLUSION

Targeting Fel d 1 to FcgammaRI induces a novel variation of the T(H)2 response that incorporates major elements of a protective T-cell response.

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.

Prevalence and titer of IgE antibodies to mouse allergens

BACKGROUND

Positive skin tests to allergens derived from mouse urine have been reported among patients with asthma. Very few data are available detailing the titer of IgE Ab to mouse allergen and how it varies by location and population.

OBJECTIVE

To evaluate further the prevalence and titer of IgE Ab to mouse-derived allergens and their relevance to total IgE and asthma.

METHODS

IgE Ab to mouse allergens was measured in 1165 sera from diverse populations including children and adults. The results were compared with IgE Ab to other allergens and total serum IgE.

RESULTS

Positive results were found in 79 sera, but only 15 had an IgE Ab titer >or=10 IU/mL. Results for IgE Ab to Mus m 1 showed a close quantitative correlation with IgE Ab to mouse allergen (r = 0.93; P < .001). Cohorts in neither Atlanta nor Virginia contained sera in which IgE Ab to mouse was dominant over other allergens or contributed significantly to total IgE. By contrast, among 319 mothers from minority groups in Boston, 11 sera had >or=10 IU/mL. In these sera, specific IgE Ab to mouse made a significant contribution to the total.

CONCLUSION

Mouse allergen sensitization may contribute significantly to total IgE and allergy in African American and Hispanic populations from some northern cities. Analysis of the significance of an IgE Ab response should include quantitative comparison with other responses and total IgE.

CLINICAL IMPLICATIONS

Significance of rodent infestation and IgE Ab varies dramatically in different populations and areas of the United States.

Defining the T cell antigen proteome of wasp venom

BACKGROUND

While modulation of T cell function is believed to be important in the successful acquisition of clinical tolerance during venom immunotherapy, little is known of the role of wasp venom specific T cell antigens.

OBJECTIVE

We sought comprehensively to characterize the T cell proteome for wasp venom to facilitate the future development of T cell-based immunotherapeutic approaches.

METHODS

Using peripheral blood mononuclear cells from wasp venom-allergic individuals and IL-4 ELISPOT analysis, we characterized T cell responses to whole venom and gel filtration/ion exchange-fractionated venom. Reactive fractions were purified and identified using highly sensitive electrospray ion-trap mass spectrometry.

RESULTS

Wasp venom-allergic individuals have detectable whole wasp venom-specific T cells directly ex vivo, which show rapid IL-4 effector function. T cell responses to gel filtration/ion exchange fractionated venom were dominated by responses to phospholipase A(1), hyaluronidase and antigen 5.

CONCLUSION

Although it is likely that there are many T cell antigens within wasp venom, the main responses are to proteins coincident with the known IgE-binding proteins.

Suppression of TH2-type allergic reactions by helminth infection

There is no immunological mechanism to adequately explain the sudden epidemic in allergies noted in the last 30 years in developed countries. The reduction in the development of allergic disorders observed in individuals infected with parasitic helminths, however, supports a possible role for worms in suppressing allergies. Helminths regulate the immunity of the host to ensure a mutually beneficial environment for the survival of both the parasite and the host. This interplay between helminths and allergic responses raises fundamental questions in immunobiology. Harnessing current mechanistic studies for translational research into helminth infections and atopy might have potential for the identification of novel biomarkers, and even therapeutics, in allergic diseases.

T-cell responses to allergens

The allergic response in human beings is engineered by CD4(+) T lymphocytes, which secrete T(H)2 cytokines in response to activation by allergen-derived peptides. Although T(H)2 cells have been well characterized, defining the properties of allergen-specific T cells has proved challenging in human beings because of their low frequency within the T-cell repertoire. However, recent studies have provided insight into the molecular signature of long-lived human memory T(H)2 cells, which are allergen-specific. T-cell responses directed against allergens develop in early life and are heavily influenced by the type and dose of allergen, and possibly coexposure to microbial products. These responses are susceptible to suppression by regulatory T cells. This article highlights recent advances in the characterization of allergen-specific memory T(H)2 cells and discusses the heterogeneous nature of regulatory T cells and possible mechanisms of action. The relevance of T-cell epitope mapping studies to understanding the unique nature of T-cell responses to different allergens, as well as to peptide vaccine development, is reviewed. Experimental techniques and approaches for analyzing allergen-specific T cells and identifying novel T-cell epitopes are described that may lead to new T-cell-based therapies.

Contribution of dust mite and cat specific IgE to total IgE: relevance to asthma prevalence

BACKGROUND

The prevalence of asthma is strikingly different in some Westernized countries: approximately 20% in New Zealand and approximately 8% in northern Sweden.

OBJECTIVE

We investigated differences in total IgE and in the prevalence of wheezing related to the observation that high exposure to dust mite allergens induces high titers of IgE antibodies.

METHODS

Two age-matched, population-based cohorts-1155 children in New Zealand (224 sera) and 3431 children (797 sera) in the Norrbotten area of Sweden-were studied. Sera were assayed for total IgE and specific IgE antibodies to relevant allergens.

RESULTS

The mean total IgE among wheezing children was higher in New Zealand than Sweden (218 IU/mL vs 65.2 IU/mL; P < .001). In addition, the prevalence of high titer specific IgE antibody (> or =50 IU/mL) was greater among the wheezing children in New Zealand compared with Sweden (35.7% vs 13.0%; P < .001). Specific IgE antibody to mite in New Zealand was significantly related to high total IgE (> or =200 IU/mL; r = 0.47; P < .001), whereas the IgE antibody response to cat allergens did not make a significant contribution to high total IgE in either country.

CONCLUSION

The quantity of IgE antibody produced to dust mite provides a possible explanation for the higher total IgE levels found in children in New Zealand and may help to explain the differences in prevalence and severity of asthma between these 2 countries.

CLINICAL IMPLICATIONS

Specific IgE antibody responses to dust mite and cat allergens may contribute differently to total serum IgE and to the prevalence of allergic disease.

Interleukin-4 promotes human CD8 T cell expression of CCR7

Despite strong evidence supporting a pathway of human T cell differentiation characterized by changes in the expression of CCR7, CD28, CD27 and CD62L, few studies have addressed the mechanisms of pathway regulation. Cutaneous lymphocyte-associated antigen (CLA)-positive skin-homing CD8(+) T cells expressed significantly elevated levels of activation markers compared with CLA(-) CD8(+) T cells in individuals (n = 27) with cutaneous atopic disease. Despite such an activated phenotype, CLA(+) T cells expressed significantly higher levels of CCR7 than a CLA(-) T cell subset. Interleukin (IL)-4 was found to dramatically promote CCR7 expression by antigen-specific CD8(+) cells. Furthermore, skin-homing CD8(+) T cells from individuals with severe disease produced significantly less IL-10 than those derived from mildly affected atopic subjects. Thus in a T-helper 2 dominated disease, tissue-specific CD8(+) T cells show altered CCR7 expression and cytokine production, which may contribute to continued lymph node homing, antigen presentation and disease. IL-4 promotes expression of CCR7, a marker linked to existing models of CD8(+) T cell differentiation.

Prospects for peptide-based immunotherapy for dog allergy

PURPOSE OF REVIEW

Tolerance to ubiquitous environmental substances, allergens, can be accomplished with specific immunotherapy. Conducting therapy with allergen peptides helps to avoid immediate allergic reactions. Dogs are a source of important indoor allergens, which necessitates the development of effective modes of therapy against the allergy they cause.

RECENT FINDINGS

The human T-cell epitopes of the major dog allergen Can f 1 were determined recently. They were found to be distributed in seven epitope regions along the molecule. For the peptide immunotherapy of dog allergy, using a pool of seven peptides, one from each of the epitope regions of Can f 1, seems at present to be the best approach. As Can f 1 is not as immunodominant as the main allergens of some other mammals, it remains to be seen whether peptides from other dog allergens should be included in the pool.

SUMMARY

The use of a pool of seven peptides from the T-cell epitope regions of Can f 1 is likely to be feasible for treating dog allergy in a great majority of Caucasian populations. In the future, patient-tailored preparations of variants of the T-cell epitope-containing peptides may offer a way to enhance the efficacy of peptide-based immunotherapy.

Interleukin-10-secreting type 1 regulatory T cells in rodents and humans

Interleukin-10 (IL-10)-secreting T regulatory type 1 (Tr1) cells are defined by their specific cytokine production profile, which includes the secretion of high levels of IL-10 and transforming growth factor-beta(TGF-beta), and by their ability to suppress antigen-specific effector T-cell responses via a cytokine-dependent mechanism. In contrast to the naturally occurring CD4+ CD25+ T regulatory cells (Tregs) that emerge directly from the thymus, Tr1 cells are induced by antigen stimulation via an IL-10-dependent process in vitro and in vivo. Specialized IL-10-producing dendritic cells, such as those in an immature state or those modulated by tolerogenic stimuli, play a key role in this process. We propose to use the term Tr1 cells for all IL-10-producing T-cell populations that are induced by IL-10 and have regulatory activity. The full biological characterization of Tr1 cells has been hampered by the difficulty in generating these cells in vitro and by the lack of specific marker molecules. However, it is clear that Tr1 cells play a key role in regulating adaptive immune responses both in mice and in humans. Further work to delineate the specific molecular signature of Tr1 cells, to determine their relationship with CD4+ CD25+ Tregs, and to elucidate their respective role in maintaining peripheral tolerance is crucial to advance our knowledge on this Treg subset. Furthermore, results from clinical protocols using Tr1 cells to modulate immune responses in vivo in autoimmunity, transplantation, and chronic inflammatory diseases will undoubtedly prove the biological relevance of these cells in immunotolerance.

The DR4-DQ8 haplotype and a specific T cell receptor Vbeta T cell subset are associated with absence of allergy to Can f 1

BACKGROUND

The significance of specific T cell receptor (TCR) Vbeta subtypes and human leucocyte antigen (HLA) class II alleles for the development of allergy to lipocalin allergens such as the major dog allergen Can f 1 is not clear at present.

OBJECTIVE

To characterize the TCR Vbeta usage in the Can f 1-specific T cell lines and the HLA class II genotypes of Can f 1-allergic and non-allergic subjects.

METHODS

T cell lines were induced with recombinant Can f 1 from the peripheral blood mononuclear cells of 12 non-atopic dog owners and 26 dog-allergic patients. Thirteen of the dog-allergic subjects were sensitized to Can f 1. Expression of the TCR Vbeta subtypes on CD4(+) T cells in the T cell lines was measured by flow cytometry. The subjects were HLA genotyped for DRB1, DQB1 and DPB1 loci.

RESULTS

Can f 1-specific T cell lines were obtained from 18 subjects, with either positive (n=8) or negative (n=10) skin prick tests (SPTs) to recombinant Can f 1. The frequency of TCR Vbeta5.1(+) T cells was significantly higher in the T cell lines of subjects with negative SPTs to the allergen. Moreover, DR4-DQ8 haplotype was over-represented among these subjects.

CONCLUSION

The DR4-DQ8 haplotype and the TCR Vbeta5.1(+) CD4(+) T cells may be protective against allergy to Can f 1.

Characterization of T cell epitopes in alphas1-casein in cow's milk allergic, atopic and non-atopic children

BACKGROUND

One to two percent of infants suffer from IgE-mediated allergic reactions against cow's milk proteins. Most children develop clinical tolerance, but approximately 15% are still allergic by the age of 10 years. Little is known about the T cell epitopes in individual cow's milk protein in relation to allergy and tolerance.

OBJECTIVE

To identify T cell epitopes in alphas1-casein, the most abundant milk protein, and to investigate T cell responses toward these epitopes in allergic, atopic and non-atopic children.

METHODS

Allergen-specific T cell lines (TCLs) were derived from peripheral blood mononuclear cells of 11 cow's milk allergic, nine atopic and nine non-atopic children. T cell responses were measured to alphas1-casein and to overlapping peptides (18-mers), spanning the alphas1-casein molecule. Proliferation was determined by incorporation of (3)H-thymidine, and cytokine production (IL-10, IL-13 and IFN-gamma) was measured by ELISA.

RESULTS

Four main regions (amino acid (AA) residues 43-66, 73-96, 91-114 and 127-180) in the alphas1-casein molecule were immunogenic to T cells, among which the AA residues 133-156 spanned the immunodominant part. Only subtle differences were found in peptide recognition between the subject groups. Some of the peptides induced slightly Th1- or Th2-skewed cytokine responses. The increased levels of IL-10 in response to alphas1-casein observed in TCLs from atopic children appeared not to be linked to recognition of specific IL-10-inducing epitopes.

CONCLUSIONS

The immunodominant sequence in alphas1-casein is spanned by AA residues 133-156. Tolerance towards alphas1-casein in atopic children may be mediated by an overall induction of IL-10 and not by recognition of certain T cell epitopes. The identified T cell epitopes in children with cow's milk allergy may be useful targets in developing peptide immunotherapy.

Sublingual immunotherapy with Dermatophagoides monomeric allergoid down-regulates allergen-specific immunoglobulin E and increases both interferon-gamma- and interleukin-10-production

BACKGROUND

The clinical efficacy and safety of sublingual immunotherapy (SLIT) for aeroallergens has been demonstrated in several trials, whereas the immunological changes induced by this treatment, which may account for the clinical improvement, are still unclear.

OBJECTIVE

To investigate the effects of a successful SLIT on the in vitro allergen-driven T cell response and cytokine secretion as well as on the serum levels of chemokines and of IgE, IgG1 and IgG4 antibodies (Abs).

MATERIALS AND METHODS

Twenty-five Dermatophagoides pteronyssinus (Dp)-sensitive patients with perennial rhinitic and/or rhinitic and asthmatic symptoms were randomized into two groups (13 untreated (UT) and 12 SLIT-treated) for a 1 year and half study. The proliferative response of peripheral blood mononuclear cell (PBMC) to purified Der p1 allergen, their cytokines (IFN-gamma, IL-4, IL-10 and TGF-beta) production and serum levels of chemokines associated with T helper type 1 (Th1) (CXCL10) or T helper type 2 (Th2) (CCL22) responses and of Dp-specific IgE, IgG1 and IgG4 Abs were evaluated before and after 6 months of treatment.

RESULTS

SLIT induced a significant reduction of symptom medication scores after 6, 12 and 18 months of treatment in comparison with UT patients. SLIT-treated patients showed a significant decrease in serum levels of DP-specific IgE Abs, whereas total IgE, and specific IgG1 and IgG4 Abs remained unchanged. The proliferative response of allergen-specific T cells to Der p1 in vitro after 6 months of treatment was reduced, while no effect was observed on T cell proliferation to recall antigen (streptokinase). Moreover, Der p1-driven IFN-gamma and IL-10 were significantly increased in culture supernatants of PBMC from 6 month-treated patients in comparison with those detected at the beginning of therapy.

CONCLUSIONS

These data suggest that the allergen-driven enhancement of IL-10- and IFN-gamma-producing T cells precedes and associates with SLIT-induced down-regulation of specific IgE, thus providing a rationale to explain the clinical benefit of SLIT in allergic patients.

Mouse allergen-specific immunoglobulin G4 and risk of mouse skin test sensitivity

BACKGROUND

High serum levels of cat-specific IgG and IgG4 are associated with protection against allergic sensitization to cat, but whether this association applies to other animal allergens remains unclear.

OBJECTIVE

To determine if high levels of mouse-specific IgG and IgG4 are associated with a decreased risk of mouse skin test sensitivity.

METHODS

Two hundred and sixty workers of a mouse facility underwent skin prick testing and completed a questionnaire. Serum levels of mouse-specific IgG and IgG4 were quantified by solid-phase antigen binding assays. Room air samples were collected and airborne Mus m 1 was quantified by ELISA.

RESULTS

Forty-nine participants had a positive skin prick test to mouse. Mouse-specific IgG was detected in 219 (84%) participants and IgG4 was detected in 72 (28%) participants. A detectable mouse-specific IgG4 level was associated with an increased risk of mouse skin test sensitivity (odds ratios (OR) 6.4, 95% confidence intervals (CI) 3.3-12.4). Mouse-specific IgG and IgG4 were both positively correlated with mouse allergen exposure (r(s)=0.31, P=0.0001, and r(s)=0.27, P=0.0006, respectively). The odds of skin test sensitivity peaked at moderate levels of IgG4, but decreased at the highest levels of mouse-specific IgG4. In contrast, the odds of skin test sensitivity increased monotonically with IgG levels.

CONCLUSIONS

A detectable level of mouse-specific IgG4 is associated with an increased risk of skin test sensitivity to mouse. However, the highest IgG4 levels appear to be associated with an attenuated risk of mouse skin test sensitivity, suggesting that induction of high levels of IgG4 through natural exposure may protect against the development of allergic sensitization.

Selective roles and dysregulation of interleukin-10 in allergic disease

There is mounting evidence to support a role for interleukin (IL)-10 in the regulation of both allergic and nonallergic immune responses. The current view is that IL-10 influences Th2-driven allergic processes by altering the interplay between Th1 and Th2 effector cells. However, lack of a clear delineation of the different types of IL-10-secreting regulatory T cells poses a major challenge in defining IL-10-mediated immune pathways, which govern the development, persistence, and modulation of allergic status. This is compounded by observations that undermine the credibility of the Th1/Th2 paradigm as a model for allergic disease. Nevertheless, enhanced IL-10 secretion by T cells during conventional immunotherapy, coupled with evidence of a link between genetics and high IL-10 production to a specific allergen, suggests that IL-10 induction is an appropriate goal of therapy. Knowledge of the targeted patient population and design of an immunogen (ie, peptide or modified allergen) within this context are likely to provide improved results over conventional immunotherapy.

Severe atopic dermatitis is associated with a reduced frequency of IL-10 producing allergen-specific CD4+ T cells

BACKGROUND

Several studies have investigated levels of T-cell-derived interleukin (IL)-10 in individuals with atopic dermatitis, with conflicting results.

AIMS/HYPOTHESIS

In order to address whether stratification of disease severity may help resolve the different findings, the hypothesis was tested that individuals with severe atopic dermatitis have a lower frequency of circulating IL-10-producing, allergen-specific CD4+ T cells than do individuals with mild disease.

METHODS

Using peripheral blood mononuclear cells derived from individuals with severe (n=12) and mild atopic dermatitis (n=10) and from nonatopic controls (n=10), we investigated production by CD4+ T cells of tumour necrosis factor (TNF)-alpha, IL-4, IL-5, IL-13 and IL-10 in response to phorbol myristate acetate/ionomycin and Der p1 allergen.

RESULTS

It was observed that there were significantly higher frequencies of allergen-specific circulating CD4+ T cells producing TNF-alpha- IL-4-, IL-5- and IL-13, and lower frequencies of these cells producing IL-10 in individuals with severe atopic dermatitis compared with mildly affected individuals and nonatopic controls (P<0.01 for all comparisons). Furthermore, the Der p1-specific CD4+ T cells were enriched within the subset of cells positive for cutaneous lymphocyte-associated antigen.

CONCLUSIONS

Analysis of levels of allergen-specific CD4+ T-cell production of IL-10 in relation to disease severity argues in favour of a role for IL-10 in the control of atopic dermatitis.

Allergen-specific MHC class II tetramer+ cells are detectable in allergic, but not in nonallergic, individuals

Allergen-specific cells are present in very low frequency in peripheral blood of humans, and differ in function in allergic and nonallergic individuals. We report in this study that soluble class II MHC tetramers can be used to directly identify and study such allergen epitope-specific CD4+ T cells in humans. We identified the major antigenic epitope of rye grass allergen Lol p 1 in HLA-DRB1*0401 individuals using HLA-DR*0401 transgenic mice and peripheral blood cells from HLA-DR*0401 individuals. Using DRB1*0401 tetramers loaded with this major epitope of Lol p 1, we detected allergen-specific CD4+ T cells in the peripheral blood of DRB1*0401 rye grass allergic individuals after ex vivo expansion with allergen. These tetramer-positive cells produced IL-4, but little IFN-gamma. In contrast, we were unable to detect rye grass tetramer-positive cells in cultures from HLA-DR*0401 nonallergic individuals, even after expansion with IL-2. Thus, our results suggest that rye grass allergen-specific T cells in DR*0401 nonallergic subjects are present at very low levels (e.g., because of deletion or suppression), differ in a fundamental way in their requirement for ex vivo expansion (e.g., they may be anergic), or use TCRs distinct from those of allergic individuals. Thus, analysis using DRB1*0401 tetramers loaded with a major epitope of Lol p 1 indicates that allergen-specific CD4+ T cells in nonallergic individuals are distinct from those in allergic subjects.

How exposures to biologics influence the induction and incidence of asthma

A number of environmental factors can affect the development and severity of allergy and asthma; however, it can be argued that the most significant inhaled agents that modulate the development of these conditions are biologics. Sensitization to environmental allergens is an important risk factor for the development of asthma. Innate immune responses are often mediated by receptors on mononuclear cells whose primary ligands arise from microorganisms. Many pathogens, especially viruses, target epithelial cells and affect the host immune response to those pathogens. The acquired immune response to an allergen is influenced by the nature of the innate immune system. Products of innate immune responses to microbes promote T(H)1-acquired responses. In the absence of T(H)1 responses, T(H)2 responses can dominate. Central to T(H)1/T(H)2 balance is the composition of contaminants that derive from microbes. In this review we examine the biology of the response to allergens, viruses, and bacterial products in the context of the development of allergy and asthma.

Tr1 cells: from discovery to their clinical application

Peripheral tolerance is mediated by multiple mechanisms such as anergy and/or active suppression of effector T cells by T regulatory (Tr) cells. Among the CD4(+) Tr cells, T regulatory type 1 cells (Tr1) have been shown to down-modulate immune responses through production of the immunosuppressive cytokines IL-10 and TGF-beta. Tr1 cells maintain peripheral tolerance, control autoimmunity, and prevent allograft rejection and graft versus host disease (GvHD). Cellular therapy with ex vivo generated Tr1 cells has been proven to be effective in several preclinical models of T cell-mediated pathologies and therefore, represents a promising approach for clinical application. This review will summarize the new findings on Tr1 cells, the recent development of methods for their ex vivo expansion, and their potential clinical relevance as cellular therapy.

Is the hygiene hypothesis still a viable explanation for the increased prevalence of asthma?

The hygiene hypothesis states that a reduced exposure to allergens in early life is solely implicated in the growing propensity for allergy sensitization. Important elements of the hypothesis include helminth infection, exposure to endotoxins, exposure to pets and growing up on a farm. However, the hygiene hypothesis alone does not provide an adequate explanation for the observed increase in allergic disease. For example, in North American inner cities, asthma is increasing among children who live in very poor housing, which might be assumed to be somewhat dirty. In order to explain the increase in asthma, we need to take a broader view and also consider alterations related to the adoption of a western lifestyle. It has been suggested that lifestyle changes related to obesity (e.g. a change in diet) are associated with asthma. Other changes include a progressive decrease in physical activity. This lifestyle factor seems to correlate best with the recent increase in asthma. Clearly, the link between physical activity and asthma needs to be investigated in more detail.

Genetic and respiratory tract risk factors for aspergillosis: ABPA and asthma with fungal sensitization

Allergic bronchopulmonary aspergillosis (ABPA) is a Th2 allergic hypersensitivity lung disease due to bronchial colonization of Aspergillus fumigatus that affects 1-2% of asthmatic and 7-9% of cystic fibrosis (CF) patients. We hypothesize that genetic risk factors predispose these patients to develop ABPA. We previously reported HLA-DR2 and DR5 restriction as a risk factor for the development of ABPA. We further propose that HLA-DR restriction is necessary but not sufficient for the development of ABPA. Recently, we reported that IL-4Rα single nucleotide polymorphisms (SNP) and in particular the ile75val SNP in the IL-4 binding region is another risk factor and is associated with increased sensitivity to IL-4 stimulation. It has been reported that the combination of IL-4Rα and IL-13 SNP, ile75val/arg110gln, is associated with more severe asthma. In preliminary studies, we have observed increased frequency of this combination in ABPA asthmatic and CF patients. Another genetic risk factor reported by Brouard et al. is the -1082 GG genotype in the IL-10 promoter in CF patients for the colonization of A. fumigatus and development of ABPA. This genotype was associated with increased plasma IL-10 levels, and perhaps may be associated with increased skewing of Th2 Aspergillus responses rather than down-regulation of inflammatory responses. We hypothesize that increased sensitivity of IL-4 mediated activities secondary to polymorphisms IL-4R in conjunction of other polymorphisms such as IL-13 and IL-10 in conjunction with HLA-DR2/DR5 restriction to Aspergillus antigens in ABPA patients result in increased B-cell activity, monocyte/dendritic cell phenotype that skews Th2 responses, and skewing of Aspergillus-specific Th2 cells. This model system may be applicable to other fungi such as Alternaria and Cladosporium which is associated with increased asthma severity.

Molecular design of allergy vaccines

Recombinant-allergen-based diagnostic tests enable the dissection and monitoring of the molecular reactivity profiles of allergic patients, resulting in more specific diagnosis, disease monitoring, prevention and therapy. In vitro experiments, animal studies and clinical trials in patients demonstrate that allergenic molecules can be engineered to induce different immune responses ranging from tolerance to vigorous immunity. The available data thus suggest that molecular engineering of the disease-related antigens is a technology that may be applicable not only for the design of allergy vaccines but also for the design of vaccines against infectious diseases, autoimmunity and cancer.

Phenotypic and functional differences between human CD4+CD25+ and type 1 regulatory T cells

T regulatory (Tr) cells have an essential role in the induction and maintenance of tolerance to both and foreign self-antigens. Many types of T cells with regulatory activity have been described in mice and humans, and those within the CD4+ subset have been extensively characterized. CD4+ Type-1 regulatory T (Tr1) cells produce high levels of IL-10 and mediate IL-10-dependent suppression, whereas the effects of naturally occurring CD4+CD25+ Tr cells appear to be cell-contact-dependent. Tr1 cells arise in the periphery upon encountering antigen in a tolerogenic environment. In contrast, it appears that CD4+CD25+ Tr cells can either arise directly in the thymus or be induced by antigen in the periphery. We have been interested in defining the phenotype and function of different subsets of CD4+ Tr cells present in human peripheral blood, with the ultimate aim of designing therapeutic strategies to harness their immunoregulatory effects. This review will discuss the similarities and differences between human Tr1 and naturally occurring CD4+CD25+ Tr cells, as well as evidence that indicates that they have nonoverlapping, but synergistic roles in immune homeostasis.

High-dose allergen exposure leads to tolerance

Reports of decreased sensitization to cat allergen (Fel d 1) among individuals living with a cat or subjects exposed to high-dose cat allergen may be explained by the development of a form of high-dose tolerance resulting from natural exposure to an inhalant allergen. Although the epidemiological data regarding the relationship between exposure and sensitization to Fel d 1 are conflicting, the ability for high-dose Fel d 1 to induce a characteristic nonallergic immune response with a distinctive serum antibody profile has been established. Definition of this modified T-helper (Th)2 response to cat allergen, coupled with the renewed interest in regulatory T cells within the immunology field, has provided an avenue for exploring the mechanism by which IgE antibody-mediated responses are controlled. There is mounting evidence to suggest that the modified Th2 response is a variation of the allergic response and that the modified Th2-allergic axis is influenced by allergen dose and genetics. This article discusses putative immune mechanisms of tolerance within the context of an allergen-specific system. The relevance of high-dose allergen exposure and alternate factors such as endotoxin to the development of tolerance is considered. Fel d 1 exhibits unique molecular and immunological characteristics that may contribute to its tolerogenic properties. Major T-cell epitopes of Fel d 1 that preferentially induce regulatory factors have been defined. Furthermore, high-titer IgE antibody responses associated with atopic dermatitis are characterized by a defect in the T-cell repertoire that is specific to these epitopes. Identification of Fel d 1 epitopes that induce interleukin-10 may provide new targets for treatment.

A new paradigm for immunoglobulin E in allergic diseases

Recent observations at the level of the antigen presenting cell, as well as the T cell, point toward a pivotal role for interleukin (IL)-10 in the control of immunoglobulin E (IgE)-mediated allergic diseases, such as asthma and rhinitis. This has led to restructuring of the Th1/Th2 paradigm with IL-10 acting to modulate Th2-driven IgE antibody (Ab) responses. The modified Th2 response to cat allergen is associated with high-dose allergen exposure and the presence of high titer IgG and IgG4 Ab; however, IgE Ab and allergic symptoms are absent. Characteristics of this immune response indicate that it is a variant of the allergic response, which develops in an IL-10-dependent manner, but it is distinct from other types of nonallergic or tolerant responses. These observations point toward a new paradigm for the development of IgE-mediated responses. This may be important for advancing our understanding of the response to immunotherapy and anti-IgE, and for defining immune mechanisms that drive allergic responses.

Characterization of the alloreactive helper T-cell response to the platelet membrane glycoprotein IIIa (integrin-beta3) in human platelet antigen-1a alloimmunized human platelet antigen-1b1b women

BACKGROUND

The aims were to characterize the helper T-cell response to platelet (PLT) glycoprotein (GP) IIIa, which stimulates the alloimmune antibody response to human PLT antigen (HPA)-1a, to identify immunodominant epitopes and to examine the HLA Class II associations.

STUDY DESIGN AND METHODS

Peripheral blood mononuclear cells (PBMNCs) were obtained from 21 HPA-1b1b women who had an HPA-1a-mismatched pregnancy, 14 of whom developed anti-HPA-1a, and 11 control donors. PBMNCs were stimulated with two panels of 15-mer peptides corresponding to the HPA-1a/1b polymorphic region, with either Leu33 (-1a) or Pro33 (-1b) at each possible position, and the proliferative responses were measured. HLA Class II and HPA genotyping was by conventional polymerase chain reaction-sequence-specific priming.

RESULTS

Peptides with Leu33 at, or near, the C-terminus contained an immunodominant epitope, stimulating proliferation by helper T cells from all nine women who had anti-HPA-1a at the time of testing; peptide L1 (Val19-Leu33) stimulated a response in 50 percent of these women. Their T cells did not respond to the corresponding HPA-1b Pro33 peptides, and responses to either peptide panel were rare in unimmunized women and controls. HLA-DRB3*01+ was significantly overrepresented (p = 0.014) in alloimmunized women whose T cells responded to the major HPA-1a Leu33-containing epitope. Conversely, HLA-DRB1*15 was negatively associated (p = 0.014) with this response.

CONCLUSIONS

The HPA-1a polymorphic region of GPIIIa contains both the linear T-cell and the conformational B-cell epitopes. The immunodominant T-cell epitope is constrained by HLA-DRB3*01+, and if presented by a tolerogenic route, a peptide containing this epitope may form the basis for the prevention or reversal of the alloimmune response to HPA-1a.

Initial high-dose nasal allergen exposure prevents allergic sensitization to a neoantigen

Primary allergic sensitization--IgE formation after Ag exposure--is fundamental in the development of allergic respiratory disease. With the rising prevalence of asthma and allergic rhinitis, improved understanding of the determining factors for allergic sensitization is needed. Human epidemiologic studies suggest high-dose allergen exposure may paradoxically protect against sensitization. Prospective human studies of allergen dose effect on primary allergic sensitization are lacking. We prospectively examined the effect of respiratory Ag dose exposure on the rate of primary allergic sensitization to a neoantigen, keyhole limpet hemocyanin, using a unique model of human nasal allergic sensitization. Atopic human subjects were exposed to 0.1-, 10-, 1,000-, or 100,000-mug doses of intranasal keyhole limpet hemocyanin in conjunction with adjuvant intranasal diesel exhaust particles. Ag-specific IgE, IgG, and IgG4 were measured in nasal lavage samples at the conclusion of the sensitization protocol. Allergic sensitization rates for the 0.1-, 10-, 1,000-, and 100,000-mug dose groups were 0, 100, 57, and 11%, respectively. All subjects produced Ag-specific IgG with the highest levels observed in the high-dose group. These results provide direct evidence that primary allergic sensitization may be prevented by initial high levels of respiratory Ag exposure through induction of a modified, nonallergic immune response. This Ag dose effect was capable of overcoming the well-established allergic adjuvant effects of diesel exhaust particle exposure. Whether this immune response represents durable allergic tolerance is not yet known. Studies investigating the molecular mechanisms of this non-IgE response may be useful in developing therapy to prevent allergic sensitization.

Targeting memory Th2 cells for the treatment of allergic asthma

Th2 memory cells play an important role in the pathogenesis of allergic asthma. Evidence from patients and experimental models indicates that memory Th2 cells reside in the lungs during disease remission and, upon allergen exposure, become activated effectors involved in disease exacerbation. The inhibition of memory Th2 cells or their effector functions in allergic asthma influence disease progression, suggesting their importance as therapeutic targets. They are allergen specific and can potentially be suppressed or eliminated using this specificity. They have distinct activation, differentiation, cell surface phenotype, migration capacity, and effector functions that can be targeted singularly or in combination. Furthermore, memory Th2 cells residing in the lungs can be treated locally. Capitalizing on these unique attributes is important for drug development for allergic asthma. The aim of this review is to present an overview of therapeutic strategies targeting Th2 memory cells in allergic asthma, emphasizing Th2 generation, differentiation, activation, migration, effector function, and survival.

Longitudinal study on the relationship between cat allergen and endotoxin exposure, sensitization, cat-specific IgG and development of asthma in childhood--report of the German Multicentre Allergy Study (MAS 90)

BACKGROUND

Controversial data have emerged regarding the question whether cat exposure in childhood favours or decreases the risk of sensitization and allergic airway disease. In a prospective birth-cohort study, we assessed the association between longitudinal cat allergen exposure, sensitization (immunoglobulin E, IgE), IgG antibody (ab) levels to cat and the development of asthma in children up to the age of 10 years.

METHODS

Of 1314 newborn infants enrolled in five German cities in 1990, follow-up data at age 10 years were available for 750 children. Assessments included yearly measurements of specific serum IgE to cat and at age 6 and 18 months, 3, 4 and 10 years measurement of cat allergen Fel d 1 in house dust samples. Additionally, Fel d 1-specific IgG ab were determined in 378 serum samples of 207 children. Endotoxin exposure in mattress dust was measured in a subgroup of 153 children at age 10 years. From age 4 years on, International Study of Asthma and Allergy in Childhood (ISAAC) questionnaires were completed yearly in order to assess the prevalence of wheeze and asthma.

RESULTS

Serum IgG-levels to cat showed a large variation, however, intraindividually values showed rather constant concentration over a longer time period. The IgG levels at school-age correlated with cat allergen exposure during the first 2 years of life. Specific IgE to cat was clearly associated with wheeze ever, current wheeze and bronchial hyperresponsiveness (BHR), this was also observed for children with specific IgE ab to cat (>0.35 kU/l) plus IgG levels above 125 U/ml. A large percentage of very highly exposed children showed high IgG but no IgE responses to cat, however, not all highly exposed children were found to be protected from sensitization. Children with IgG but without IgE ab to cat showed the lowest prevalence of wheeze ever and current wheeze despite high cat allergen exposure, however, this trend did not achieve significance. While homes of cat owners showed higher Fel d 1 concentrations than homes without cats, homes of cat owners were not found to have higher endotoxin levels in carpet dust samples than homes without cats.

CONCLUSIONS

We could confirm that high cat allergen exposure in a cohort with lower community prevalence of cats is associated with higher serum IgG and IgE levels to cat in schoolchildren. Sensitization to cat allergen (IgE) is a risk factor for childhood asthma. While exposure to cat allergen during infancy is associated with sensitization (IgE), only in the very highly exposed children the likelihood of sensitization (IgE) is decreased and high IgG levels to cat without IgE were associated with low risk of wheeze. However, cat-specific IgG ab levels did not protect children with IgE-mediated sensitization from wheeze.

Production of interleukin 10 and transforming growth factor beta in concomitant allergy and autoimmunity

BACKGROUND

The immunologic relationship between T(H)1-type autoimmune disorders and T(H)2-type allergic disorders and the role of T-cell regulation in humans is as yet unclear. The regulatory cytokine production capacity of individuals with concomitant allergy and T(H)1-type autoimmunity may provide insight into the role of T-cell regulation in both disorders.

OBJECTIVES

To examine the production capacity of interleukin 10 (IL-10) and transforming growth factor beta (TGF-beta), 2 regulatory cytokines, in individuals with concomitant allergic rhinitis and T(H)1-type autoimmune diagnoses and to compare that capacity with that in individuals with allergic rhinitis only and individuals with neither diagnosis.

METHODS

Seventeen case subjects and 17 age-, sex-, and ethnicity-matched controls with allergic rhinitis only were recruited from an allergy clinic. Fourteen matched controls with neither diagnosis were recruited from the general population. Peripheral blood mononuclear cells were obtained and cultured with and without mitogen stimulation (lipopolysaccharide and phytohemagglutinin). Cytokine levels from culture supernatants were measured by enzyme-linked immunosorbent assay.

RESULTS

Cases with allergic rhinitis and autoimmune diseases had significantly lower unstimulated day 3 IL-10 levels compared with controls with allergic rhinitis only (P = .05) and significantly lower stimulated day 5 TGF-beta levels compared with controls with neither diagnosis (P = .02). Cases had consistently lower regulatory capacity compared with both control groups, as measured by an additive index using IL-10 and TGF-beta levels.

CONCLUSION

Individuals with concomitant allergic rhinitis and T(H)1-type autoimmune disorders have a lower regulatory cytokine production capacity than individuals with allergic rhinitis only and those with neither diagnosis.

Allergens

Exposure to allergens is a trigger for symptoms in sensitized individuals with asthma. This is especially true for allergens primarily found indoors but can be true for outdoor allergens with sufficiently high exposure. The role of allergens in attacks can be subtle in that they provide the underlying inflammation necessary for other nonspecific agents to have an effect.

Allergy and dermatophytes

Tinea pedis (athlete's foot) and onychomycosis (infection of the toenails) caused by the dermatophyte fungus Trichophyton are highly prevalent in adults. Several Trichophyton allergens have been identified based on elicitation of immunoglobulin E antibody-mediated immediate-hypersensitivity (IH) responses. Evidence of an etiologic role for Trichophyton in asthma in some subjects with IH and chronic dermatophytosis is provided by bronchial reactivity to Trichophyton. Improvement of asthma after systemic antifungal treatment corroborates this link. A unique feature of Trichophyton allergens is the ability of the same antigen to elicit delayed-type hypersensitivity (DTH) in individuals who lack IH reactivity. Delayed responses appear to confer protection, while IH responses do not, based on the association with acute versus chronic skin infection. The amino acid sequence identity of Trichophyton allergens with diverse enzyme families supports a dual role for these proteins in fungal pathogenesis and allergic disease. Characterizing the immunologic properties of Trichophyton allergens and defining immune mechanisms which drive dichotomous responses are pivotal to understanding the dermatophyte-allergy relationship. Recent studies have identified DTH-associated major T-cell epitopes which could facilitate the development of peptide vaccines. Characterization of additional molecular targets by using new techniques may aid not only in the eradication of infection but also in the resolution of allergic symptoms.

T cell epitope immunotherapy induces a CD4+ T cell population with regulatory activity

BACKGROUND

Synthetic peptides, representing CD4(+) T cell epitopes, derived from the primary sequence of allergen molecules have been used to down-regulate allergic inflammation in sensitised individuals. Treatment of allergic diseases with peptides may offer substantial advantages over treatment with native allergen molecules because of the reduced potential for cross-linking IgE bound to the surface of mast cells and basophils.

METHODS AND FINDINGS

In this study we address the mechanism of action of peptide immunotherapy (PIT) in cat-allergic, asthmatic patients. Cell-division-tracking dyes, cell-mixing experiments, surface phenotyping, and cytokine measurements were used to investigate immunomodulation in peripheral blood mononuclear cells (PBMCs) after therapy. Proliferative responses of PBMCs to allergen extract were significantly reduced after PIT. This was associated with modified cytokine profiles generally characterised by an increase in interleukin-10 and a decrease in interleukin-5 production. CD4(+) cells isolated after PIT were able to actively suppress allergen-specific proliferative responses of pretreatment CD4(neg) PBMCs in co-culture experiments. PIT was associated with a significant increase in surface expression of CD5 on both CD4(+) and CD8(+) PBMCs.

CONCLUSION

This study provides evidence for the induction of a population of CD4(+) T cells with suppressor/regulatory activity following PIT. Furthermore, up-regulation of cell surface levels of CD5 may contribute to reduced reactivity to allergen.

Asthma severity and prevalence: an ongoing interaction between exposure, hygiene, and lifestyle

Why are the prevalence and severity of asthma increasing? Platts-Mills looks at the key studies that can help to anwer this important question

Asthma and indoor air: contrasts in the dose response to cat and dust-mite

The role of the indoor environment in asthma is of major concern because (i) the disease has become more severe; (ii) we spend>or=90% of our lives indoors and (iii) a large proportion of asthmatic children and young adults are allergic to allergens found indoors. Recent evidence that children raised in a home with animals, i.e. indoor cat or dog, are less likely to become allergic has provided a great opportunity to understand the mechanisms controlling the prevalence of allergic disease. In addition the results pose a challenge to many of the hypotheses about reasons for the increase in asthma. The evidence that children or adults who make a modified TH2 response i.e. immunoglobulin (Ig)G and IgG4 ab without IgE, are not at increased risk of asthma strongly supports the role of IgE in asthma. Equally the results may give insight into a form of tolerance that could be a target for protecting patients against allergic disease.

PRACTICAL IMPLICATIONS

Evidence for the immune response to cat allergen shows that the alternative response to an allergy, TH2 response, is a controlled or modified form of the response not a Th1 response. Furthermore, avoiding cats in the home in most communities would not decrease the prevalence of sensitization to cats because there is cat allergen distributed in schools, other public buildings, and homes without a cat.

Molecular characterization of major cat allergen Fel d 1: expression of heterodimer by use of a baculovirus expression system

Fel d 1 is a major cat allergen inducing allergic rhinitis and asthma in sensitized individuals. It has a more complex structure when compared with other allergens and therefore expression of recombinant Fel d 1 has been considered a challenge. The present study shows for the first time that a Baculovirus expression system is able to produce an intact rFel d 1 molecule that is glycosylated and structurally equivalent to the natural cat allergen, nFel d 1. Enzymatic digestion of rFel d 1 and further analysis by use of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) resulted in a complete coverage of the amino acid sequence of rFel d 1. In addition, the three disulfide bridges at the positions alpha70-beta7, alpha44-beta48, and alpha3-beta73 were verified. The N-glycan structure of rFel d 1 was investigated by a combination of MALDI-TOF MS and monosaccharide analysis by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAC). The N-glycosylation analyses of rFel d 1 refer to a pattern of glycoforms including core alpha1.3-fucosylation that is different from nFel d 1. Further characterization by use of human serum IgE, histamine release, and lymphocyte proliferation assays demonstrated that the immunological characteristics of rFel d 1 are similar to those of nFel d 1. Detailed characterization of both natural and recombinant allergens provides tools to explore immunological mechanisms associated with allergen sensitization and desensitization.

T cell epitope-specific defects in the immune response to cat allergen in patients with atopic dermatitis

Atopic dermatitis (AD) is often associated with high titer IgE antibodies (ab) to allergens, and IL-10-mediated regulation of IFN-gamma has been proposed to contribute to this IgE ab production. However, the relevance of IL-10 and IFN-gamma to IgE associated with AD has not been examined in the context of an allergen-specific system. Analysis of PBMC responses in vitro showed deficient T cell proliferation to overlapping IL-10- (peptide (P) 2:1) and IFN-gamma- (P2:2) inducing chain 2 major epitopes of cat allergen (Fel d 1) in cultures from sensitized AD patients (mean IgE to cat=20.9 IU/ml). Diminished IFN-gamma induction by Fel d 1 and P2:2, along with elevated peptide-induced IL-10 (except for P2:1) was observed in PBMC cultures from AD subjects compared with non-AD (sensitized and non-sensitized) subjects. Neither T cell proliferation nor IFN-gamma production to chain 2 epitopes could be restored by anti-IL-10 mAb in cultures from sensitized AD subjects. Moreover, allergen avoidance was associated with a paradoxical decrease in both IL-10 and IFN-gamma in peptide-stimulated PBMC from these subjects. Control of IFN-gamma production to chain 2 epitopes by IL-10 may be relevant to sensitization status. Development of high titer IgE ab in AD could reflect a failure of this mechanism.