Antigen-bearing dendritic cells from the sublingual mucosa recirculate to distant systemic lymphoid organs to prime mucosal CD8 T cells.

Effector T cells are described to be primed in the lymph nodes draining the site of immunization and to recirculate to effector sites. Sublingual immunization generates effector T cells able to disseminate to the genital tract. Herein, we report an alternative mechanism that involves the recirculation of antigen-bearing dendritic cells (DCs) in remote lymphoid organs to prime T cells. Sublingual immunization with a muco-adhesive model antigen unable to diffuse through lymphatic or blood vessels induced genital CD8 T cells. The sublingual draining lymph nodes were not mandatory to generate these lymphocytes, and antigen-bearing DCs from distant lymph nodes and spleen were able to prime specific CD8 T cells in a time- and dose-dependent manner. This study demonstrates, for the first time, that antigen-bearing DCs originating from the site of immunization recirculate to distant lymphoid organs and provides insights into the mechanism of distant CD8 T-cell generation by sublingual immunization.