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Updated: May 5, 2026
Isolation and Flow Cytometric Characterization of Murine Small Intestinal Lymphocytes
Published on: May 8, 2016
Innate immune functions of α-defensins in the small intestine
1Department of Microbiology and Immunology, School of Medicine, University of California Davis, Davis, Calif., USA.
Abstract:
The intestinal mucosa interfaces with a complex, dense community of microorganisms, including hundreds of species of resident microbiota and many transient microbes entering from food- and water-borne sources. In the small intestine, Paneth cells (specialized secretory epithelial cells) produce abundant quantities of α-defensins and several other antibiotic peptides. Human Paneth cells make two α-defensins: HD5 and HD6. Data from in vivo models indicate that Paneth cell α-defensins play a pivotal role in defense from food- and water-borne pathogens in the intestine. The mechanism by which these two α-defensins protect from enteric pathogens is quite distinct. HD5 is a potent antimicrobial that kills target microbes by membrane disruption, whereas HD6 is newly discovered to self-assemble to form fibrils and nanonets that surround and entangle bacteria. Recent data suggest that HD5 also serves to help shape the composition of the colonizing microbiota. Studies in humans suggest that reduced expression of HD5 and HD6 is a fundamental feature of ileal Crohn's disease. Mechanistically, the link between reduced Paneth cell α-defensin expression and ileal Crohn's disease pathogenesis may be a result of the weakened mucosal antimicrobial defense and/or alterations in the composition of commensal microbiota.
Insights
Paneth cells in the small intestine produce alpha-defensins (HD5 and HD6) crucial for gut defense. Reduced expression of these antimicrobial peptides is linked to ileal Crohn
Area of Science:
- Microbiology and Immunology
- Gastroenterology
- Cell Biology
Background:
- The intestinal mucosa harbors a dense microbial community, necessitating robust defense mechanisms.
- Paneth cells, specialized epithelial cells in the small intestine, secrete antimicrobial peptides, including two human alpha-defensins: HD5 and HD6.
Purpose of the Study:
- To elucidate the distinct antimicrobial mechanisms of HD5 and HD6.
- To investigate the role of Paneth cell alpha-defensins in shaping gut microbiota composition.
- To explore the association between reduced HD5/HD6 expression and ileal Crohn's disease pathogenesis.
Main Methods:
- In vivo models were utilized to assess the function of Paneth cell alpha-defensins.
- Mechanistic studies were performed to differentiate the antimicrobial actions of HD5 and HD6.
- Human studies examined the expression levels of HD5 and HD6 in relation to ileal Crohn's disease.
Main Results:
- HD5 exhibits potent antimicrobial activity through direct membrane disruption of target microbes.
- HD6 self-assembles into fibrils and nanonets, effectively ensnaring and entangling bacteria.
- HD5 also plays a role in modulating the composition of the intestinal microbiota.
- Reduced expression of both HD5 and HD6 is a characteristic feature observed in the ileum of Crohn's disease patients.
Conclusions:
- Paneth cell alpha-defensins HD5 and HD6 employ distinct mechanisms to defend the intestine against pathogens.
- Altered expression of these alpha-defensins may contribute to Crohn's disease by compromising mucosal defense and/or microbiota homeostasis.
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