Hairy guide to maintaining T_RM cells

Mammalian skin has long-term resident populations of memory T cells (T_RM cells). In Nature Medicine, Nagao and colleagues demonstrate that hair follicles are directly responsible for the maintenance of T_RM cells in the skin. Certain keratinocytes that line the hair follicles of both humans and mice express interleukin 7 (IL-7) and IL-15. Production of IL-15 by hair follicles is required specifically for the maintenance of CD8⁺ T_RM cells but is dispensable for CD4⁺ T_RM cells. However, follicular expression of IL-7 is necessary for the presence of both CD4⁺ T_RM cells and CD8⁺ T_RM cells in the skin. The absence of either of these cytokines impairs contact hypersensitivity or, for IL-7, impairs the accumulation of skin T cells in a model of cutaneous T cell lymphoma. These findings indicate that particular populations of follicle keratinocyte have an essential role in controlling the homeostasis of T_RM cells.

Nat. Med. (19 October 2015) doi:10.1038/nm.3962