Memory T cell formation and phenotype varies across intestinal compartments

Area of Science:

• Immunology
• Gastroenterology
• Cell Biology

Background:

• Tissue-resident memory T (T_RM) cells are crucial for intestinal immunity following infection.
• Most research on intestinal T_RM cells focuses on the small intestine (SI), with limited understanding of T_RM cell formation in the large intestine (LI).

Purpose of the Study:

• To compare the abundance and phenotype of memory T cells across different intestinal compartments (SI vs. LI).
• To investigate the role of TGF-β signaling in T_RM cell heterogeneity within the gastrointestinal tract.

Main Methods:

• Comparative analysis of memory T cell populations in mouse models of infection.
• Phenotypic characterization of T cells in the epithelium and lamina propria of the SI and LI.
• Loss- and gain-of-function studies to assess TGF-β signaling dependencies.

Main Results:

• Fewer memory T cells formed in the LI compared to the SI.
• LI T_RM cells, including Ly6C-expressing CD8⁺ T_RM cells, exhibited distinct phenotypes and cytokine/granzyme profiles compared to SI counterparts.
• Ly6C⁺CD103- T_RM cells developed independently of TGF-β in both SI and LI.
• Enhanced TGF-β signaling preferentially expanded Ly6C^- T_RM populations in the LI, but not the SI, indicating compartment-specific regulation.

Conclusions:

• Regional differences in the gastrointestinal tract significantly influence T_RM cell development, phenotype, and function.
• TGF-β signaling plays a critical role in establishing T_RM cell heterogeneity between the SI and LI.
• These findings highlight the importance of considering anatomical location when studying intestinal T_RM cell immunity.