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.

Keywords:

• Mucosal immunity
• Paneth cells
• host defense
• defensins
• lectins
• mucins
• sIgA

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Funding

The authors thank the NIH [Grant DP2OD007045 from the Office of the Director] and the MIT Department of Chemistry for supporting our research on human enteric α-defensin peptides. P. C. is a recipient of a Royal Thai Government Fellowship.