Human resident memory T cells hit the road

Skin and other barrier tissues are home to long-lived tissue-resident memory T cells (T_RM) that function as sentries capable of rapidly responding to previously encountered antigens. Klicznik et al. investigated the relationship between human skin CD4⁺ T_RM and human blood CD4⁺ memory T cells expressing skin-homing markers by comparing immunophenotypes, gene expression, and T cell receptor sequences. Shared phenotype, function, and clonotypes between blood and skin CLA⁺CD103⁺CD4⁺ T cells indicated that blood CD4⁺CLA⁺CD103⁺ T cells were previously skin resident. Analysis of immunodeficient mice bearing human skin xenografts revealed that human skin CD4⁺ T_RM can exit the skin, reenter the circulation, and home to secondary human skin sites. These findings establish that there is basal recirculation of human CD4⁺ skin T_RM.

https://immunology.sciencemag.org/content/4/37/eaav8995