Deficient Resident Memory T Cell and CD8 T Cell Response to Commensals in Inflammatory Bowel Disease

Area of Science:

• Immunology
• Gastroenterology
• Microbiome research

Background:

• The gut microbiota interacts closely with resident memory lymphocytes in mucosal tissues.
• Understanding immune responses to the microbiota is crucial for distinguishing health from inflammatory bowel disease (IBD).

Purpose of the Study:

• To investigate differences in acquired cellular and humoral immunity to the microbiota in healthy individuals versus those with IBD.
• To analyze resident memory T cells (Trm) and local antibody responses in the colon.

Main Methods:

• Analysis of colonic biopsies for resident memory T cells (Trm).
• Assessment of local antibody responses to intraepithelial microbes.
• Evaluation of systemic antigen-specific T and B cell memory to commensal microbes.

Main Results:

• Healthy individuals exhibit systemic CD4 and some CD8 T cell responses to gut bacteria, with limited B cell memory.
• IBD patients show decreased CD8 T cell responses but increased B cell responses and plasmablasts.
• IBD is associated with reduced mucosal CD8+ Trm and γδ T cells, alongside increased IgA responses to intraepithelial bacteria.
• Colonic Trm express CD39 and CD73, indicating regulatory function, and their interaction with dendritic cells influences T-bet expression.

Conclusions:

• IBD presents an imbalance between cellular and humoral immunity, characterized by diminished T cell-mediated barrier immunity and heightened antibody responses.
• The regulatory function of Trm may be linked to intestinal health.
• Strategies promoting Trm and their interaction with dendritic cells, rather than immunosuppression, could enhance tissue immunity and barrier function in IBD.