Intestinal epithelial barrier and mucosal immunity

Abstract

Intestinal mucosa integrates primary digestive functions with immune functions such as pathogen surveillance, antigen transport and induction of mucosal immunity and tolerance. Intestinal adaptive immunity is elicited in organized mucosa-associated lymphoid tissue (O-MALT) that is composed of antigen-presenting cells and lymphocytes and achieved by effector cells widely distributed in mucosa (diffuse MALT or D-MALT). Interaction between the intestinal epithelium, the O-MALT and the diffuse MALT plays a critical role in establishing an adequate immune response. In regions associated to O-MALT, lympho-epithelial cross-talks lead to acquisition of a specific epithelial phenotype that contributes to O-MALT organization and functionality. Beyond the expression of several innate immune functions, the intestinal epithelium may directly take up and present antigens due to the expression of major histocompatibility complex (MHC) and MHC-related molecules. A complex genetic program that will be outlined in the present review controls the development of immune functions of the intestinal epithelium. The effect of environmental signals on the modulation of this ontogenetic program during development and neonatal life, from bioactive components of amniotic fluid to lactation and bacterial colonization, will be discussed.

Antibiotics, Pediatric Dysbiosis, and Disease

“…For example, goblet cells, responsible for mucin production, are functional by 12 weeks of gestation (Montgomery et al, 1999), as are paneth cells, which can secrete defensins and lysozymes by gestational weeks 13 and 20, respectively (Louis and Lin, 2009; Maheshwari and Zemlin, 2009; Rumbo and Schiffrin, 2005). Although full-term infants are born with fully developed digestive tracts, exogenous stimulation through exposure to dietary antigens, hormones, growth factors, and bacteria is required to elicit proper function throughout life (Forchielli and Walker, 2005).…”

Breast Milk Oligosaccharides: Structure-Function Relationships in the Neonate

“…However, at birth the neonate’s gastrointestinal tract is functionally immature and immune incompetent (112), although it is confronted with an increasing antigenic load in the form of dietary proteins, commensal organisms, and pathogens. The single layer of enterocytes that line the intestinal epithelium forms a functional barrier between the luminal contents of the gut and the infant’s circulatory system.…”

Pathogenesis of NEC: Role of the innate and adaptive immune response

“…Ontogeny studies have demonstrated that Paneth cells can be detected by 12 weeks gestation and begin to produce antimicrobial defensins at 13 weeks and lysozyme at 20 weeks 199,200 . Significant HD5 expression can be detected at above 29 weeks 201 .…”