Development pathway for skin resident memory CD103+CD8+ T cells

Tissue resident memory T cells (TRM) provide superior protection against infection localised to extra-lymphoid compartments in the body. Here we show that CD103+CD8+ TRM cells develop in skin from killer cell lectin-like receptor (KLR)G1-negative precursors that selectively infiltrate the epithelial layer. In the skin, a combination of chemokine-guided epithelial entry, local interleukin (IL)-15 and transforming growth factor (TGF)-β signalling is required for formation and survival of these long-lived memory cells. Importantly, TRM differentiation results in the gradual acquisition of a unique transcriptional profile that differs from that expressed by memory cells in the circulation and other types of skin-resident intra-epithelial T cells, such as the dendritic epidermal T cells (DETC). We provide a comprehensive molecular and developmental framework for the local differentiation of a distinct type of peripheral memory T cell that contributes to an important first-line of immune defence in barrier tissues such as skin and mucosa. 24 samples were analyzed: 3 replicates of memory gB-T CD8+. CD103+ T cells isolated from the skin of C57/BL6 mice on day 30 p.i. with HSV KOS. 3 replicates of memory P14 CD8+ T cells isolated from gut of mice on day 60 p.i. with LCMV Armstrong. 3 replicates of memory gB-T CD8+ T cells from the lung of mice on day 30 p.i. with influenza WSN. 3 replicates of memory CD62L high CD8+ T cells from the spleen of mice on day 30 p.i. with HSV KOS. 3 replicates of memory CD62L low CD8+ T cells from the spleen of mice of day 30 p.i. with HSV KOS. 3 replicates of γδ-DETC isolated from the skin of C57/BL6 mice on day 30 p.i. with HSV KOS. 3 replicates of αβ-DETC from naive TCRδ-/- mice; and 3 replicates of naive gB-T CD8+ T cells from the spleen of naive gB-T transgenic mice.