PD-1 regulates ILC3-driven intestinal immunity and homeostasis

Area of Science:

• Immunology
• Gastroenterology
• Cell Biology

Background:

• Interleukin-22 (IL-22) production by intestinal group 3 innate lymphoid cells (ILC3) is essential for gut homeostasis.
• Dysregulated IL-22 levels are linked to intestinal epithelial barrier defects and tumor development.
• Programmed cell death 1 (PD-1) is a known immune checkpoint, primarily studied in cancer and chronic infection.

Purpose of the Study:

• To identify genes associated with IL-22 production in ILC3.
• To investigate the role of PD-1 expression on ILC3 in gut homeostasis and inflammation.
• To characterize the functional and metabolic properties of PD-1 expressing ILC3.

Main Methods:

• Single-cell RNA sequencing to identify gene expression patterns in ILC3.
• Analysis of PD-1 expression on ILC3 under various conditions (microbiota, inflammation, IL-23, Notch ligand).
• Assessment of ILC3 function, metabolism, proliferation, and reactive oxygen species levels.
• Experimental models of colitis to evaluate the role of PD-1 in vivo.

Main Results:

• A subset of ILC3 constitutively expressed PD-1 and exhibited enhanced IL-22 production capacity.
• PD-1 expression on ILC3 was influenced by microbiota, IL-23, and Notch signaling.
• PD-1+ ILC3 displayed distinct metabolic profiles, increased proliferation, and enhanced antioxidant capacity.
• Loss of PD-1 signaling in ILC3 impaired IL-22 production and gut barrier function during inflammation.
• PD-1 deficiency on ILC3 increased susceptibility to experimental colitis.

Conclusions:

• PD-1 signaling plays a novel, critical role in regulating IL-22 production by ILC3.
• PD-1+ ILC3 are important for maintaining gut barrier integrity and immune homeostasis.
• Targeting PD-1 on ILC3 may offer therapeutic potential for inflammatory gut diseases.