Abstract
Adaptive immunity relies on antibodies and memory B and T cells, with memory T cells providing "reactive memory". These cells either circulate in the blood or remain as tissue-resident memory T cells, yet the epigenetic mechanisms underlying their recall function and maintenance are not well understood. Here, we present a comprehensive analysis of 56 reduced representation bisulfite sequencing (RRBS) datasets from 22 memory CD4 and CD8 T-cell populations isolated from human bone marrow, intestine, spleen, lung, skin, and peripheral blood, including surface CD69-positive and CD69-negative cells. Our study reveals unique DNA hypomethylation patterns in tissue-resident memory T cells, particularly in regions associated with genes involved in tissue homing, residency, and transcription factors regulating recall effector memory. The methylomes and differential methylation signatures identified here serve as a valuable resource for understanding the epigenetic program of memory T lymphocytes, their roles in immunological recall, and their maintenance within specific tissues. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s44466-025-00009-x.