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Updated: Oct 11, 2025
Assessing the Cellular Immune Response of the Fruit Fly, Drosophila melanogaster, Using an In Vivo Phagocytosis Assay
Published on: April 10, 2019
Intestinal FoxO signaling is required to survive oral infection in Drosophila
C Fink1, J Hoffmann1, M Knop1
1Department of Zoology, Molecular Physiology, Christian-Albrechts University Kiel, Kiel, Germany.
Abstract:
The intestinal immune system is tailored to fight pathogens effectively while tolerating the indigenous microbiota. Impairments of this homeostatic interaction may contribute to the etiology of various diseases including inflammatory bowel diseases. However, the molecular architecture underlying this complex regulatory interaction is not well understood. Here, we show that the fruit fly Drosophila melanogaster has a multilayered intestinal immune system that ensures strictly localized antimicrobial responses. Enterocytes, a major cell population of the intestine, produced antimicrobial peptides (AMPs) in a FoxO- but not NF-κB-dependent manner. Consequently, animals impaired in FoxO-mediated signaling had a significantly lowered resistance to intestinal infections; they were unable to increase the expression of AMP genes and males showed an increased bacterial load in response to an infection. Conventional innate immune signaling converging onto NF-κB activation was operative in only a few regions of the intestine, comprising the proventriculus, copper cells, and intestinal stem cells. Taken together, our results imply that danger-mediated as well as conventional innate immune signaling constitute modules that contribute to the fruit fly's intestinal immune system. We propose that this special architecture ensures localized and efficient antimicrobial responses against invasive pathogens while preserving the microbiota.
Insights
Fruit flies possess a sophisticated intestinal immune system. This system uses FoxO signaling for localized antimicrobial peptide production, enhancing pathogen defense while maintaining gut microbiota balance.
Area of Science:
- Immunology
- Gastroenterology
- Drosophila melanogaster research
Background:
- The intestinal immune system balances pathogen defense and microbiota tolerance.
- Dysregulation of this balance is implicated in inflammatory bowel diseases.
- The molecular mechanisms governing intestinal immune homeostasis are not fully understood.
Purpose of the Study:
- To elucidate the molecular architecture of the fruit fly's intestinal immune system.
- To investigate the roles of FoxO and NF-κB signaling pathways in intestinal immunity.
- To understand how localized antimicrobial responses are achieved.
Main Methods:
- Utilized Drosophila melanogaster as a model organism.
- Investigated antimicrobial peptide (AMP) gene expression in enterocytes.
- Analyzed the impact of FoxO and NF-κB signaling disruptions on infection resistance.
- Examined bacterial load in response to infection.
Main Results:
- Enterocytes produce AMPs in a FoxO-dependent, NF-κB-independent manner.
- Impaired FoxO signaling reduces resistance to intestinal infections and AMP gene expression.
- NF-κB-dependent innate immune signaling is restricted to specific intestinal regions.
- Fruit flies exhibit a multilayered intestinal immune system with localized responses.
Conclusions:
- FoxO-mediated signaling is crucial for localized antimicrobial responses in the fruit fly intestine.
- Both danger-mediated and conventional innate immune signaling contribute to intestinal immunity.
- This specialized architecture enables targeted pathogen elimination while preserving the gut microbiota.
