Dendritic cells govern induction and reprogramming of polarized tissue-selective homing receptor patterns of T cells: important roles for soluble factors and tissue microenvironments.

Tissue-selective homing is established during naive T cell activation by the tissue microenvironment and tissue-specific dendritic cells (DC). The factors driving induction and maintenance of T cell homing patterns are still largely unknown. Here we show that soluble factors produced during the interaction of T cells with CD11c(+) DC isolated from skin- or small intestine-associated tissues differentially modulate expression of the corresponding tissue-selective homing receptors (E-selectin ligands and alpha4beta7 integrin/CCR9, respectively) on murine CD8(+) T cells. Injection of tissue-specific DC via different routes induces T cells with homing receptors characteristic of the corresponding local tissue microenvironment, independent of the origin of the DC. These data indicate an important role for signals delivered in trans. Moreover, DC can reprogram the homing receptor expression on T cells previously polarized in vitro for homing to skin or small intestine. Importantly, skin-homing memory T cells stimulated directly ex vivo can also be reprogrammed by intestinal DC to a gut-homing phenotype. Our results show that tissue-selective homing receptor expression on effector and memory T cells is governed by inductive as well as suppressive signals from both DC and tissue microenvironments.