The epithelial barrier and immunoglobulin A system in allergy

Abstract

Airway and intestinal epithelial layers represent first-line physical barriers, playing a key role in mucosal immunity. Barrier dysfunction, characterized by alterations such as disruption of cell-cell apical junctions and aberrant epithelial responses, probably constitutes early and key events for chronic immune responses to environmental antigens in the skin and in the gut. For instance, barrier dysfunction drives Th2 responses in atopic disorders or eosinophilic esophagitis. Such epithelial impairment is also a salient feature of allergic asthma and growing evidence indicates that barrier alterations probably play a driving role in this disease. IgA has been identified as the most abundant immunoglobulin in mucosa, where it acts as an active barrier through immune exclusion of inhaled or ingested antigens or pathogens. Historically, it has been thought to represent the serum factor underlying reaginic activity before IgE was discovered. Despite several studies about regulation and major functions of IgA at mucosal surfaces, its role in allergy remains largely unclear. This review aims at summarizing findings about epithelial functions and IgA biology that are relevant to allergy, and to integrate the emerging concepts and the recent developments in mucosal immunology, and how these could translate to clinical observations in allergy.

Food‐specific antibodies in oesophageal secretions: association with trigger foods in eosinophilic oesophagitis

“…Forceps and brush biopsies have revealed that immunoglobulins (Immunoglobulin G4 and Immunoglobulin E) are increased in EoE tissues 21 . Although not studied specifically in EoE, Immunoglobulin A is a known mucosal exclusion antibody secreted on the gastrointestinal surface to protect the body from potential threats, such as bacteria and viruses 22 . Local reactions within diseased tissues may also involve either secretory or immune‐mediated Immunoglobulin A production as seen in celiac disease 23,24 .…”

Lactic acid bacteria-specific induction of CD4+Foxp3+T cells ameliorates shrimp tropomyosin-induced allergic response in mice via suppression of mTOR signaling

“…Innate lymphoid cells and mast cells (MCs), in particular, orchestrate the mucosal regulatory system to create a mutually beneficial environment for both the host and the microbiota 30 . Barrier dysfunction drives Th2 responses in food anaphylaxis, atopic disorders or eosinophilic esophagitis 31 . Our findings showed that LAB strains (Bc and Lp) with notable anti-allergic effect against ST sensitization greatly restored the intestinal epithelial barrier functions by improvement of gut epithelial integrity, suppression of MCs degranulation in lamina propria, and skewing of the immune response from a Th2 to a Th1 polarization in MLN.…”

Bifidobacterium bifidum OLB6378 Simultaneously Enhances Systemic and Mucosal Humoral Immunity in Low Birth Weight Infants: A Non-Randomized Study

“…Non-live OLB6378 administration could be safe and beneficial to VLBW infants. Moreover, the increase in humoral immunity through non-live OLB6378 administration to full-term infants might be useful in the prevention of infantile allergies [32]. Further studies on the effects of non-live OLB6378 administration on not only VLBW infants but also on full-term infants in the early postnatal period are warranted.…”