Vbeta18.1(+) and V(alpha)2.3(+) T-cell subsets are associated with house dust mite allergy in human subjects

Antigen-specificity measurements are the key to understanding T cell responses

Antigen-specific T cells play a central role in the adaptive immune response and come in a wide range of phenotypes. T cell receptors (TCRs) mediate the antigen-specificities found in T cells. Importantly, high-throughput TCR sequencing provides a fingerprint which allows tracking of specific T cells and their clonal expansion in response to particular antigens. As a result, many studies have leveraged TCR sequencing in an attempt to elucidate the role of antigen-specific T cells in various contexts. Here, we discuss the published approaches to studying antigen-specific T cells and their specific TCR repertoire. Further, we discuss how these methods have been applied to study the TCR repertoire in various diseases in order to characterize the antigen-specific T cells involved in the immune control of disease.

HLA-II Alleles Influence Physical and Behavioral Responses to a Whey Allergen in a Transgenic Mouse Model of Cow's Milk Allergy

The symptoms of food allergies vary significantly between individuals, likely due to genetic determinants. In humans, allergy development is initiated by antigen-presenting cells via class II human leukocyte antigen (HLA-II). The HLA-II gene is highly polymorphic, and its allelic variance is thought to influence the susceptibility of individuals to a particular allergen. However, whether antigen presentation by different HLA-II variants contributes to symptom variation is not clear. We hypothesized that HLA-II allelic variance affects symptom phenotypes, including immediate physical reactions and delayed behavioral changes, in individuals with food hypersensitivity. To test our hypothesis, male and female mice of three transgenic strains expressing an HLA-II variant, DR3, DR15, or DQ8, were used to establish a cow's milk allergy model. Mice were sensitized to a bovine whey allergen, β-lactoglobulin (BLG; Bos d 5), weekly for 5 weeks, followed by an acute oral allergen challenge. At 30 min post-challenge, BLG-sensitized DR3 mice showed moderate to severe anaphylaxis resulting in perioral redness, swelling, and death. In contrast, DQ8 and DR15 mice were generally asymptomatic. The production of allergen-specific immunoglobulins was also HLA- and sex-dependent. Both male and female DR3 and female DR15 mice significantly increased BLG-specific IgE production, while robust elevation in BLG-specific IgG1 was observed in sensitized DQ8 mice of both sexes and, to a lesser extent, in DR15 males. Furthermore, BLG-sensitized DR15 mice showed sex-specific behavior changes, with males exhibiting mobility changes and anxiety-like behavior and females showing spatial memory impairment. When splenocytes from transgenic mice were stimulated in vitro with BLG, phenotypes of immune cells were HLA- and sex-specific, further underscoring the influence of HLA-II on immune responses. Our results support that HLA-II alleles influence behavioral responses in addition to immune and physical reactions of food allergy, suggesting that certain HLA-II variants may predispose individuals to food-allergy-associated behavioral changes.

T Cell Repertoire During Ontogeny and Characteristics in Inflammatory Disorders in Adults and Childhood

Since the first day of life, a newborn has to deal with various pathogens from the environment. While passive immune protection is provided by diaplacental maternal antibodies, the development of cellular immunity is ongoing. A mature immune system should be able not only to defend against pathogens, but should also be able to differentiate between self- and non-self-antigens. Dysregulation in the development of cellular immunity can lead to severe disorders like immunodeficiency, autoimmunity and chronic inflammation. In this review, we explain the role of T cell immunity in antigen detection and summarize the characteristics of a mature TCR repertoire as well as the current state of knowledge about the development of the TCR repertoire in ontogenesis. In addition, methods of assessments are outlined, with a focus on the advantages and disadvantages of advanced methods such as next generation sequencing. Subsequently, we provide an overview of various disorders occuring in early childhood like immunodeficiencies, autoimmunity, allergic diseases and chronic infections and outline known changes in the TCR repertoire. Finally, we summarize the latest findings and discuss current research gaps as well as potential future developments.

Interaction of allergens, major histocompatibility complex molecules, and T cell receptors: a 'ménage à trois' that opens new avenues for therapeutic intervention in type I allergy

T cells are major players in the initiation and perpetuation of the allergic immune response. In this review, we summarize the current knowledge on allergen recognition by T lymphocytes and address the components of the trimeric recognition complex: T cell receptors, major histocompatibility complex molecules, and allergen-derived peptides. Furthermore, possible implications of this scientific background for future therapeutic developments are discussed.

Bias in the αβ T-cell repertoire: implications for disease pathogenesis and vaccination

The naïve T-cell repertoire is vast, containing millions of unique T-cell receptor (TCR) structures. Faced with such diversity, the mobilization of TCR structures from this enormous pool was once thought to be a stochastic, even chaotic, process. However, steady and systematic dissection over the last 20 years has revealed that this is not the case. Instead, the TCR repertoire deployed against individual antigens is routinely ordered and biased. Often, identical and near-identical TCR repertoires can be observed across different individuals, suggesting that the system encompasses an element of predictability. This review provides a catalog of αβ TCR bias by disease and by species, and discusses the mechanisms that govern this inherent and widespread phenomenon.

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

Although allergen-specific CD4(+) T cells are detectable in the peripheral blood of both individuals with or without allergy, their frequencies and phenotypes within the memory as well as naïve repertoires are incompletely known. Here, we analyzed the DRB1*0401-restricted responses of peripheral blood-derived memory (CD4(+)CD45RO(+)) and naïve (CD4(+)CD45RA(+)) T cells from subjects with or without allergy against the immunodominant epitope of the major cow dander allergen Bos d 2 by HLA class II tetramers in vitro. The frequency of Bos d 2(127-142)-specific memory T cells in the peripheral blood-derived cultures appeared to be higher in subjects with allergy than those without, whereas naïve Bos d 2(127-142)-specific T cells were detectable in the cultures of both groups at nearly the same frequency. Surprisingly, the TCR avidity of Bos d 2(127-142)-specific T cells of naïve origin, as assessed by the intensity of HLA class II tetramer staining, was found to be higher in individuals with allergy. Upon restimulation, long-term Bos d 2(127-142)-specific T-cell lines generated from both memory and naïve T-cell pools from individuals with allergy proliferated more strongly, produced more IL-4 and IL-10, and expressed higher levels of CD25 but lower levels of CXCR3 than the T-cell lines from individuals without allergy, demonstrating differences also at the functional level. Collectively, our current results suggest that not only the memory but also the naïve allergen-specific T-cell repertoires differ between individuals with or without allergy.

Engineering of major house dust mite allergens Der p 1 and Der p 2 for allergen-specific immunotherapy

BACKGROUND

Specifically designed recombinant allergens with reduced IgE reactivity are promising candidates for a more defined, effective, and safer specific immunotherapy (SIT).

OBJECTIVE

We sought to obtain hypoallergenic hybrid molecules which could potentially be applied to house dust mite (HDM) allergy treatment.

METHODS

Two hybrid molecules (QM1 and QM2) derived from the two major Dermatophagoides pteronyssinus allergens, Der p 1 and Der p 2, were engineered by PCR, produced in Escherichia coli, and purified. The overall IgE-binding capacity of the hybrids was compared with their single components by Western blot, specific IgE, skin prick test (SPT), and IgE-inhibition assays. T cell proliferation assay were performed to confirm their retention of T cell reactivity. Immune responses to the hybrid molecules were studied in BALB/c mice.

RESULTS

The IgE reactivity of both hybrid proteins was strongly reduced as evaluated by in vitro methods. Furthermore, in vivo SPTs performed on 106 HDM-allergic patients showed that the hybrid proteins had a significantly lower potency to induce cutaneous reactions than the individual components. Hybrid molecules induced higher T cell proliferation responses than those produced by an equimolecular mixture of Der p 1 and Der p 2. Immunization of mice with the hybrid proteins induced Der p 1- and Der p 2-specific IgG, which inhibited the binding of allergic patients' IgE to these natural allergens.

CONCLUSION

QM1 and QM2 hybrids exhibited less IgE-binding activity but preserved immunogenicity and fulfilled the basic requirements for hypoallergenic molecules suitable for a future SIT of HDM allergy.

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.

T and B cell responses to HDM allergens and antigens

House dust mites provide well-characterized proteins to study human responses to inhaled antigens. Even in the absence of allergy they induce a high frequency of T cell precursors. The healthy response manifests by T cell proliferation and Th1 cytokines with little antibody. Responses of allergic people include Th1 and Th2 cytokines and IgE, IgG1, and IgG4 antibodies. Regulatory cells limit effector responses in healthy people. About half the IgE and IgG antibodies bind the group 1 and 2 allergens and 30% bind the group 4, 5, and 7 allergens. Although HLA independent, the recognition of the group 1 allergen shows an immunodominant region and a T cell receptor bias. The major allergens are not produced in higher amounts than many of the poorly non-allergenic proteins. The non-allergenic mite ferritin antigen shows high T cell proliferative responses with mixed cytokine production.

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.

Transgenic mice expressing the T cell antigen receptor specific for an immunodominant epitope of a major allergen of house dust mite develop an asthmatic phenotype on exposure of the airways to allergen

BACKGROUND

Current studies on mechanisms underlying allergen-induced pulmonary inflammation and asthma are hampered by the lack of appropriate physiological in vivo models that reflect the natural route of allergen exposure and sensitization.

OBJECTIVE

To generate and phenotype a transgenic mouse strain expressing the T cell receptor (TCR) specific for an immunodominant domain of the major inhalant allergen Dermatophagoides pteronyssinus species of house dust mite (Der p 1), for the development of an in vivo model of allergic asthma.

METHODS

Der p 1 transgenic mice were generated using TCR-alphabeta derived from a CD4+ T cell hybridoma reactive with Der p 1 residues p 110-131. The frequency and functional activity of peripheral T cells were determined and parameters of airway inflammation assessed following allergen challenge of the airways with Der p 1.

RESULTS

CD4+ T cells are functionally active, exhibiting dose-dependent proliferation and IL-4 production on primary stimulation with Der p 1 or Der p 1, p 110-131 in vitro, independent of in vivo antigen priming. On sensitization of the airways with allergen, in the absence of systemic priming or the application of adjuvants, the TCR transgenic mice develop airway inflammation characterized by a marked lymphocytic and eosinophilic infiltrate with goblet cell hyperplasia and enhanced mucin production.

CONCLUSION

The Der p 1 TCR transgenic mice provide a model for investigating the pathophysiological mechanisms of pulmonary inflammation following sensitization by exposure of the airways to allergen and for investigating the mode of action and efficacy of novel immunotherapeutics.

T-Cell and chemokine receptor variation in South Amerindian populations

The immune response of relatively small, endogamous populations is of special interest, because they may differ from those of large, ethnically diverse, urban groups. As a contribution to this area of investigation, we tested 99 individuals from two Brazilian native populations for two T-cell receptor gene segments (TCRBV3S1 and TCRBV18) and 241 subjects from eight tribes of this ethnic group in relation to the chemokine receptor CCR5delta32 allele. Differences in TCRBV3S1 and TCRBV18 prevalences of the Amerindians in relation to European- and African-derived individuals were not marked. We confirmed the absence of the CCR5delta32 allele in most groups, its presence in the Mura and Kaingang, probably because of European gene introgression.

The effect of specific immunotherapy on T-cell receptor repertoire in patients with allergy to house-dust mite

BACKGROUND

The precise mechanism of specific immunotherapy (SIT), long used for treating allergic diseases, remains undefined. SIT was shown to act by modifying the immune response of T lymphocytes to antigens. We examined the effect of SIT on the expression and use V-alpha, -beta, -gamma and -delta chains of T-cell receptors (TCR) in patients allergic to house-dust mite.

METHODS

Peripheral venous blood was taken for lymphocyte TCR analysis from 10 house-dust mite (HDM) allergic adults before initiating SIT and 6 months after initiating the treatment. Twelve similarly allergic patients without SIT served as controls. TCR chains were identified by fluorescence-activated cell sorter (FACS) using the following monoclonal antibodies: CD3, CD14, CD8, pan alpha-beta, pan gamma-delta, V-alpha2, V-alpha12.1, V-beta5a, V-beta5b, V-beta5c, V-beta8a, V-beta8b, V-beta3.1, V-beta13, V-beta12, V-beta6.7, V-delta1, V-delta2, V-gamma9, and V-gamma4.

RESULTS

Analyzed before and 6 months after SIT initiation, lymphocyte TCR showed significantly increased V-beta5b, V-beta12 and V-alpha12.1 values compared to controls (without significant changes in other markers).

CONCLUSIONS

SIT caused selective expansion of certain V-beta- and V-alpha-expressing T cells in patients allergic to HDM. Our results support the notion that the effect of SIT in patients with allergic rhinitis may be achieved by modifying the T lymphocyte response through the modulation of TCR usage.