Lymph Node Stromal Cells Support Dendritic Cell-Induced Gut-Homing of T Cells

T cells are imprinted to express tissue-specific homing receptors upon activation in tissue-draining lymph nodes, resulting in their migration to the site of Ag entry. Expression of gut-homing molecules α 4 β 7 and CCR9 is induced by retinoic acid, a vitamin A metabolite produced by retinal dehydrogenases, which are specifically expressed in dendritic cells as well as stromal cells in mucosa-draining lymph nodes. In this study, we demonstrate that mesenteric lymph node stromal cell-derived retinoic acid can directly induce the expression of gut-homing molecules on proliferating T cells, a process strongly enhanced by bone marrow-derived dendritic cells in vitro. Therefore, cooperation of sessile lymph node stromal cells with mobile dendritic cells warrants the imprinting of tissue specific homing receptors on activated T cells.