Niche-specific MHC II and PD-L1 regulate CD4+CD8αα+ intraepithelial lymphocyte differentiation

Area of Science:

• Immunology
• Gastroenterology
• Cell Biology

Background:

• Conventional CD4+ T cells differentiate into CD4+CD8αα+ intraepithelial lymphocytes (IELs) in the intestine.
• The specific roles of intestinal epithelial cells (IECs) in this differentiation process are not well understood.

Purpose of the Study:

• To investigate the role of IECs in the differentiation of CD4+ T cells into CD4+CD8αα+ IELs.
• To elucidate the molecular mechanisms by which IECs influence IEL development.

Main Methods:

• Analysis of MHC class II (MHC II) and programmed death-ligand 1 (PD-L1) expression on IECs in the distal small intestine.
• Generation of IEC-specific knockout models for MHC II and PD-L1.
• Investigation of intracellular signaling pathways, including PD-1, SHP, and ThPOK, in T cell differentiation.

Main Results:

• IECs express MHC II and PD-L1 in response to microbiota and IFN-γ in the distal small intestine.
• IEC-specific deletion of MHC II and PD-L1 significantly impaired the development of CD4+CD8αα+ IELs.
• PD-1 signaling on T cells, in conjunction with IEC-derived signals, promotes CD8αα acquisition by down-regulating ThPOK via the SHP pathway.

Conclusions:

• IECs provide essential noncanonical antigen presentation and co-stimulatory signals for the development of tissue-resident CD4+CD8αα+ IELs.
• The PD-1/SHP/ThPOK pathway is critical for CD8αα expression during IEL differentiation.
• IECs play a pivotal role in shaping the intestinal immune microenvironment by guiding T cell adaptation.