RESUMEN
BACKGROUND: IgE antibody-producing B cells are enriched in the nasal mucosa in patients with allergic rhinitis because of local class switching to IgE. The expressed IgE VH genes also undergo somatic hypermutation in situ to generate clonal families. The antigenic driving force behind these events is unknown. OBJECTIVE: To examine the possible involvement of a superantigen in allergic rhinitis, we compared the variable (VH) gene use and patterns of somatic mutation in the expressed IgE heavy-chain genes in nasal biopsy specimens and blood from allergic patients and the IgA VH use in the same biopsy specimens and also those from nonallergic controls. METHODS: We extracted mRNA from the nasal biopsy specimens of 13 patients and 4 nonallergic control subjects and PBMCs from 7 allergic patients. IgE and IgA VH regions were RT-PCR amplified, and the DNA sequences were compared with those of control subjects. We constructed a molecular model of VH5 to locate amino acids of interest. RESULTS: We observed a significantly increased frequency of IgE and IgA VH5 transcripts in the nasal mucosa of the allergic patients compared with the normal PBMC repertoire. Within IgE and IgA VH5 sequences in the nasal mucosa, the distribution of replacement amino acids was skewed toward the immunoglobulin framework regions. Three of 4 nonintrinsic hotspots of mutation identified in the VH5 sequences were in framework region 1. The hotspots and a conserved VH5-specific framework residue form a tight cluster on the surface of VH5. CONCLUSION: Our results provide evidence for the activity of a superantigen in the nasal mucosa in patients with allergic rhinitis.
Asunto(s)
Linfocitos B/inmunología , Inmunoglobulina E/genética , Cadenas Pesadas de Inmunoglobulina/genética , Región Variable de Inmunoglobulina/genética , Mucosa Nasal/inmunología , Rinitis Alérgica Perenne/inmunología , Rinitis Alérgica Estacional/inmunología , Adolescente , Adulto , Femenino , Humanos , Inmunoglobulina A/genética , Inmunoglobulina E/química , Cadenas Pesadas de Inmunoglobulina/química , Región Variable de Inmunoglobulina/química , Masculino , Persona de Mediana Edad , MutaciónRESUMEN
IgE-expressing B cells are over 1000 times more frequent in the nasal B cell than the peripheral blood B cell population. We have investigated the provenance of these B cells in the nasal mucosa in allergic rhinitis. It is generally accepted that expression of activation-induced cytidine deaminase and class switch recombination (CSR) occur in lymphoid tissue, implying that IgE-committed B cells must migrate through the circulation to the nasal mucosa. Our detection of mRNA for activation-induced cytidine, multiple germline gene transcripts, and epsilon circle transcripts in the nasal mucosa of allergic, in contrast to nonallergic control subjects, however, indicates that local CSR occurs in allergic rhinitis. The germline gene transcripts and epsilon circle transcripts in grass pollen-allergic subjects are up-regulated during the season and also when biopsies from allergic subjects are incubated with the allergen ex vivo. These results demonstrate that allergen stimulates local CSR to IgE, revealing a potential target for topical therapies in allergic rhinitis.
Asunto(s)
Alérgenos/administración & dosificación , Cambio de Clase de Inmunoglobulina , Inmunoglobulina E/genética , Mucosa Nasal/inmunología , Rinitis Alérgica Perenne/genética , Rinitis Alérgica Perenne/inmunología , Rinitis Alérgica Estacional/genética , Rinitis Alérgica Estacional/inmunología , Adulto , Linfocitos B/enzimología , Linfocitos B/inmunología , Linfocitos B/patología , Secuencia de Bases , Estudios de Casos y Controles , Citidina Desaminasa , Citosina Desaminasa/genética , Citosina Desaminasa/metabolismo , ADN Complementario/genética , Femenino , Humanos , Técnicas In Vitro , Masculino , Persona de Mediana Edad , Datos de Secuencia Molecular , Mucosa Nasal/enzimología , Mucosa Nasal/patología , ARN Mensajero/genética , ARN Mensajero/metabolismo , Rinitis Alérgica Perenne/enzimología , Rinitis Alérgica Perenne/patología , Rinitis Alérgica Estacional/enzimología , Rinitis Alérgica Estacional/patología , Homología de Secuencia de Ácido NucleicoRESUMEN
BACKGROUND: Allergic diseases are frequent and rising in prevalence, and result from activation of T-helper (Th) 2 cells by allergens. CD4+CD25+ regulatory T cells suppress T-cell activation in vitro and prevent pathological findings in animal models of disease. We aimed to investigate whether the amount of inhibition of allergic responses by CD4+CD25+ T cells was related to atopy and allergic disease. METHODS: Blood CD4+CD25+ and CD4+CD25- T cells were isolated from three groups of donors: non-atopic individuals; those atopic with no present symptoms; and patients with hayfever studied during and out of the grass-pollen season. We investigated the ability of CD25+ T cells from these donors to suppress allergen-stimulated T-cell proliferation and cytokine production in vitro. FINDINGS: CD4+CD25+ T cells from non-atopic donors suppressed proliferation and interleukin 5 production by their own allergen-stimulated CD4+CD25- T cells. Inhibition of proliferation by CD4+CD25+ T cells from atopic donors was significantly reduced (p=0.0012), and was even more diminished by CD4+CD25+ T cells isolated from patients with hayfever during the pollen season (p=0.0003). In patients with hayfever, out-of-season suppression remained less than that seen by regulatory cells from non-atopic donors. INTERPRETATION: Allergic disease can result from an inappropriate balance between allergen activation of regulatory CD4+CD25+ T cells and effector Th2 cells. This imbalance could result from a deficiency in suppression by regulatory T cells or strong activation signals could overcome such regulation. Treatment to enhance regulatory T-cell responses, in concert with reduction of Th2 cell activation, might be useful in prevention and treatment of allergic disease.
