Capacities of migrating CD1b+ lymph dendritic cells to present Salmonella antigens to naive T cells.

Dendritic cells (DCs) are well known as professional antigen-presenting cells (APC) able to initiate specific T-cell responses to pathogens in lymph nodes (LN) draining the site of infection. However, the respective contribution of migratory and LN-resident DCs in this process remains unclear. As DC subsets represent important targets for vaccination strategies, more precise knowledge of DC subsets able to present vaccine antigens to T cells efficiently is required. To investigate the capacities of DCs migrating in the lymph (L-DCs) to initiate a specific T-cell response, we used physiologically generated DCs collected from a pseudoafferent lymphatic cannulation model in sheep. The CD1b+ L-DCs were assessed for presenting antigens from the vaccine attenuated strain of Salmonella enterica serovar Abortusovis. CD1b+ L-DCs were able to phagocytose, process and to present efficiently Salmonella antigens to effector/memory T cells in vitro. They were shown to be efficient APC for the priming of allogeneic naive T cells associated with inducing both IFN-γ and IL-4 responses. They were also efficient in presenting Salmonella antigens to autologous naive T cells associated with inducing both IFN-γ and IL-10 responses. The capacities of L-DCs to process and present Salmonella antigens to T cells were investigated in vivo after conjunctival inoculation of Salmonella. The CD1b+ L-DCs collected after inoculation were able to induce the proliferative response of CD4+ T cells suggesting the in vivo capture of Salmonella antigens by the CD1b+ L-DCs, and their potential to present them directly to CD4+ T cells. In this study, CD1b+ L-DCs present potential characteristics of APC to initiate by themselves T cell priming in the LN. They could be used as target cells for driving immune activation in vaccinal strategies.