Epidermis instructs skin homing receptor expression in human T cells

ML McCully, K Ladell, S Hakobyan… - Blood, The Journal …, 2012 - ashpublications.org
Blood, The Journal of the American Society of Hematology, 2012ashpublications.org
The localization of memory T cells to human skin is essential for long-term immune
surveillance and the maintenance of barrier integrity. Although the mechanisms controlling
memory T-cell migration to peripheral tissues are poorly understood, the current paradigm
includes the localized secretion of “imprinting” signals from tissue-resident dendritic cells in
the draining lymph nodes. Here we show that CCR8 expression by newly activated naive T
cells is regulated by skin-specific factor (s) derived primarily from epidermal keratinocytes …
Abstract
The localization of memory T cells to human skin is essential for long-term immune surveillance and the maintenance of barrier integrity. Although the mechanisms controlling memory T-cell migration to peripheral tissues are poorly understood, the current paradigm includes the localized secretion of “imprinting” signals from tissue-resident dendritic cells in the draining lymph nodes. Here we show that CCR8 expression by newly activated naive T cells is regulated by skin-specific factor(s) derived primarily from epidermal keratinocytes, thereby providing a mechanism for the preferential expression of CCR8 by skin-resident memory T cells. Importantly, no such effects were observed after coculture with primary cells from skin-unrelated epithelia, including mesothelium and small intestine. The keratinocyte-derived CCR8-inducing factor(s) were soluble, and independent of vitamins A and D. Furthermore, the induction of CCR8 under these conditions correlated with an increase in cutaneous lymphocyte-associated antigen expression. Our findings challenge current tissue homing paradigms, especially those involving CCR10, and emphasize the importance of steady-state epidermis rather than tissue-resident dendritic cells in controlling the localization of memory T cells within human skin.
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