Defensins, lectins, mucins, and secretory immunoglobulin A: microbe-binding biomolecules that contribute to mucosal immunity in the human gut

Abstract

In the intestine, the mucosal immune system plays essential roles in maintaining homeostasis between the host and microorganisms, and protecting the host from pathogenic invaders. Epithelial cells produce and release a variety of biomolecules into the mucosa and lumen that contribute to immunity. In this review, we focus on a subset of these remarkable host-defense factors – enteric α-defensins, select lectins, mucins, and secretory immunoglobulin A – that have the capacity to bind microbes and thereby contribute to barrier function in the human gut. We provide an overview of the intestinal epithelium, describe specialized secretory cells named Paneth cells, and summarize our current understanding of the biophysical and functional properties of these select microbe-binding biomolecules. We intend for this compilation to complement prior reviews on intestinal host-defense factors, highlight recent advances in the field, and motivate investigations that further illuminate molecular mechanisms as well as the interplay between these molecules and microbes.

16S rRNA gene sequencing reveals an altered composition of the gut microbiota in chickens infected with a nephropathogenic infectious bronchitis virus

“…These findings suggest that NIBV infection can destroy intestinal mucosal integrity and may slow the growth of intestinal villus epithelial cells. Furthermore, it was reported that intestinal goblet cells play a crucial defensive role in the intestine by synthesizing and secreting several mediators, including mucins and trefoil factor family peptides, which serve defensive and healing functions in the gut [38][39][40] . In this study, NIBV infection obviously increased the number of goblet cells compared to that in the normal group, which indicated hyperplasia of the goblet cells in the ileum during NIBV infection and may be associated with microbial challenges.…”

Yeast fermentate prebiotic improves intestinal barrier integrity during heat stress by modulation of the gut microbiota in rats

“…Paneth and goblet cells are indispensable for maintaining homeostasis with enteric microbes (Baurhoo et al, ; Vaishnava et al, ) as they promote the removal of microbes from the mucosal surface (Chairatana and Nolan, ). Reduction in number or defects in activity of these cells lead to microbiota disbiosis (Baurhoo et al, ; Riba et al, ).…”

Proposal for an Organ-Specific Chronic Inflammation–Remodeling–Carcinoma Sequence

“…Such cells localize to the crypt base and secrete α-defensins that are essential for mucosal protection from intestinal microbial pathogens [58]. In comparison to complete intestinal metaplasia, incomplete intestinal metaplasia lacks these essential functions of Paneth cells, leading to an increased susceptibility to cellular stress and damage from various types of pathogens [59,60]. Expression of the homeobox gene Cdx2 is maintained in both incomplete and complete intestinal metaplasia, and in dysplasia.…”