Evaluation of the gut mucosal barrier: evidence for increased antigen transfer in children with atopic eczema

Abstract

Background: Intestinal antigen handling determines subsequent immune response to the antigen. Antigens are absorbed across epithelium along two functional pathways. The main pathway is degradative, which reduces the immunogenicity of the antigen. A minor pathway allows the transport of intact proteins, which is crucial for antigen-specific immune responses. The Ussing chamber method allows the quantitative measurement of protein transfer across the intestinal mucosa.

Objective: This study was designed to explore the theory that altered antigen transfer across the intestinal mucosa is a factor in the pathogenesis of atopic eczema, characterized by hyperactivity to environmental antigens.

Methods: The absorption and degradation of horseradish peroxidase (molecular weight, 40,000 d) were studied in vitro in Ussing chambers. Eighteen biopsy specimens of upper small intestinal mucosa from 14 patients (aged 0.5 to 8 years) with atopic eczema and 18 specimens from 15 age-matched control subjects were examined.

Results: The mean (95% confidence interval) absorption of intact horseradish peroxidase was significantly higher in children with atopic eczema than in control subjects: 242 (81-404) pmol . hr(-1) . cm(-2) versus 23 (12-33) pmol . hr(-1) . cm(-2); t = 2.86, p = 0.007. The absorption of degraded horseradish peroxidase was 972 (732-1213) pmol . hr(-1) . cm(-2) in patients with atopic eczema and 672 (532-811) pmol . hr(-1) . cm(-2) in control subjects; t = 2.29, p = 0.03.

Conclusions: Our results may reflect a primarily altered antigen transfer in patients who have atopic eczema, which may initiate and perpetuate prompt immune responses to common environmental antigens, including foods.