A Single D_H Gene Segment Is Sufficient for the Establishment of an Asthma Phenotype in a Murine Model of Allergic Airway Inflammation

Abstract

Background: We have previously shown that the allergic sensitization to ovalbumin does not represent a superantigen-like immune response. In gene-targeted mice (ΔD-iD) with a single modified Diversity gene segment (D_H) of the immunoglobulin heavy chain, enriched for charged amino acids, the asthma phenotype in a murine model was markedly alleviated compared to wild-type animals. Objective: We now sought to determine whether the confinement to a single D_H gene segment alone leads to a reduced allergic phenotype. Methods: We examined another gene-targeted mouse strain (ΔD-DFL) with a single D_H gene segment which encodes for neutral amino acids, thus reflecting the preferential repertoire in wild-type mice. Mice were sensitized intraperitoneally to ovalbumin. Results: Despite the constraint to a single D_H gene segment, ΔD-DFL mice mounted high total and allergen-specific IgG₁ and IgE serum levels after sensitization to ovalbumin. The affinity constants of allergen-specific IgG₁ antibodies did not differ between ΔD-DFL and wild type. Following challenge with aerosolized allergen, a marked local T_H2 cytokine response and an eosinophilic airway inflammation developed. Quantitative histology revealed increased mucus production and intense goblet cell metaplasia which were identical to those in wild type. Moreover, ΔD-DFL mice developed an airway hyperreactivity to methacholine and to the specific allergen, which both did not differ from those in wild-type animals. Conclusion: A single D_H gene segment is sufficient for the establishment of the asthma phenotype in a murine model of allergic airway inflammation. Thus, the allergic phenotype depends on the amino acid composition and not on the diversity of the classical antigen-binding site.

Airway remodeling in asthma: what really matters

“…Furthermore, since such studies revealed that airway remodeling persisted after cessation of allergen challenges well beyond the resolution of allergic inflammation, this suggests that mechanisms independent of inflammation are active in sustaining airway remodeling even when remodeling evolved as a result of allergic airway inflammation (Foster et al 2000 ; Leigh et al 2004 ; Kumar et al 2004 ). The dissociation of airway remodeling and allergic lung inflammation has additionally been supported by findings in transgenic mice as well as in studies using a therapeutic setting that reported beneficial effects on inflammatory processes whereas features of airway remodeling were not affected (Kerzel et al 2009 , 2011 ; Gregory et al 2010 ; Gabehart et al 2013 ).…”

The sequences encoded by immunoglobulin diversity (DH) gene segments play key roles in controlling B‐cell development, antigen‐binding site diversity, and antibody production

“…We also tested whether alteration of CDR‐H3 content could alter an allergic phenotyope . In mice sensitized to ovalbumin as an allergen that elicits asthma, those with a single normal D H produced total and allergen‐specific serum IgE after aerosolized antigen challenge.…”

Quantitative microscopy of the lung: a problem-based approach. Part 2: stereological parameters and study designs in various diseases of the respiratory tract

“…In rodents, airway microdissection has become the most widely used method for this purpose (81). In humans, the use of bronchoscopic biopsies to evaluate the effects of a specific asthma treatment is often employed and introduces new challenges to the stereological quantification, as the reference volume that is normally used needs to be replaced by an internal reference structure, such as the surface area of the epithelial basement membrane (47,82,113). An alternative to the global reference volume or an internal reference structure may be the use of the fractionator (27,29).…”