Tissue-Resident Memory T Cells in Chronic Inflammation-Local Cells with Systemic Effects?

Area of Science:

• Immunology
• Cell Biology
• Inflammation Research

Background:

• Chronic inflammatory diseases involve systemic and local inflammation, often with relapsing-remitting courses.
• Tissue-resident memory T cells (T_RM) are implicated in sustaining chronic inflammation within non-lymphoid tissues (NLT).
• T_RM are traditionally viewed as stationary cells within tissues.

Purpose of the Study:

• To review recent advancements regarding T_RM in chronic inflammatory diseases.
• To explore the heterogeneity and dynamic behavior of T_RM populations.
• To discuss the implications of T_RM tissue egress and circulation for diagnostics and therapeutics.

Main Methods:

• Literature review of murine and human studies on T_RM.
• Analysis of gene expression profiles associated with T_RM function and migration.
• Investigation of T_RM presence in both tissue and circulation.

Main Results:

• T_RM populations are heterogeneous, with varying functions and activation states.
• Evidence suggests T_RM can egress from NLT and enter circulation ('ex-T_RM').
• Circulating T_RM retain characteristics and propensity to re-enter specific tissues.

Conclusions:

• The paradigm of T_RM being exclusively tissue-resident is challenged.
• T_RM egress and circulation have significant implications for understanding and treating chronic inflammatory diseases.
• Circulating T_RM ('ex-T_RM') may serve as valuable biomarkers for disease diagnosis and monitoring.