From lung to gut

Intestinal CD103⁺ dendritic cells (DCs) that can metabolize vitamin A into retinoic acid induce expression of the gut-homing receptors integrin α₄β₇ and CCR9 on T cells after being activated. In the Journal of Experimental Medicine, Ruane et al. show that lung DCs can also 'imprint' the expression of gut-homing receptors in T cells and 'license' them to migrate to the gut. Both CD103⁺CD11b⁻ and CD11b⁺CD103⁻ lung DCs express aldehyde dehydrogenase and induce the expression of CCR9 and α₄β₇ on proliferating T cells in a manner dependent on signaling via the retinoic acid receptor, with lung CD11b⁺ DCs being more effective than lung CD103⁺ DCs. Intranasal delivery of antigen induces α₄β₇ expression in T cells activated in the mediastinal lymph nodes, whereas subcutaneous immunization does not confer gut-homing tropism to T cells. In in vivo models of infection with pathogenic Salmonella, intranasal immunization extends survival and averts systemic pathology.

J. Exp. Med. (19 August 1023) doi:101084/jem.20122762