Licensed delivery: The microbiota authorizes vitamin A transport.

Vitamin A derivatives imprint adaptive immune cells for small-intestinal homing, yet the microbiota's role remains unclear. In this issue, Srinivasan et al. demonstrate that the microbiota help load vitamin A derivatives onto CD11c+ myeloid cells, thereby enabling their migration to mesenteric lymph nodes, where T cells are conditioned for small-intestinal homing.