Inflammatory monocytes regulate pathologic responses to commensals during acute gastrointestinal infection

Area of Science:

• Immunology
• Microbiology
• Gastroenterology

Background:

• Commensal microbiota influence host immunity and mucosal inflammation.
• Regulation of commensal-driven inflammation during infection is not well understood.

Purpose of the Study:

• To investigate the role of inflammatory monocytes in regulating mucosal inflammation during infection.
• To elucidate the mechanisms by which inflammatory monocytes control host-commensal interactions.

Main Methods:

• Murine model of acute mucosal infection with Toxoplasma gondii.
• Analysis of inflammatory monocyte phenotype and function.
• Assessment of neutrophil activation and host pathology.
• Pharmacological modulation of prostaglandin E2 (PGE2) levels.

Main Results:

• Inflammatory monocytes acquired a regulatory phenotype producing prostaglandin E2 (PGE2) during infection.
• PGE2 produced by inflammatory monocytes inhibited neutrophil activation in a dose-dependent manner.
• Absence of inflammatory monocytes led to severe neutrophil-mediated pathology, which was ameliorated by PGE2 analog treatment.
• Inhibition of PGE2 exacerbated neutrophil activation and increased host mortality.

Conclusions:

• Inflammatory monocytes play a critical role in controlling pathogen expansion while limiting commensal-mediated gut damage.
• Monocyte-derived PGE2 is central to a regulatory loop that manages host-commensal dialogue during pathogen-induced inflammation.
• Targeting this pathway may offer therapeutic strategies for inflammatory conditions.