Characteristics of CD8+ and CD4+ Tissue-Resident Memory Lymphocytes in the Gastrointestinal Tract
Pan Li, Yixi Zhang, Yanping Xu, Hongcui Cao, Lanjuan Li
Abstract
Tissue-resident memory T cells (TRMs) are plentiful in the memory T cell pool and persist in barrier sites without recirculating. Increasing evidence has shown that some kinds of CD8+ TRMs and CD4+ TRMs are resident in the gastrointestinal tract (GI), playing an important role in the context of microbiota-immune interactions, infections, maintenance of tissue homeostasis, and tumor surveillance. Although sharing some similar phenotypes, functional properties, and transcriptional regulation with other tissue-TRMs, gastrointestinal tract TRMs (GI-TRMs) have unique phenotypic and functional characteristics reshaped by the local microenvironment. In this review, we will summarize current knowledge on the regulation, maintenance, and function of the CD8+ TRMs and CD4+ TRMs in GI, exploring how these cells contribute to local immune defense, tissue homeostasis, and tumor surveillance.