Oral dendritic cells mediate antigen-specific tolerance by stimulating TH1 and regulatory CD4+ T cells

Background: A detailed characterization of oral antigen-presenting cells is critical to improve second-generation sublingual allergy vaccines. Objective: To characterize oral dendritic cells (DCs) within lingual and buccal tissues from BALB/c mice with respect to their surface phenotype, distribution, and capacity to polarize CD4+ T-cell responses. Methods: lit situ analysis of oral DCs was performed by immunohistology. Purified DCs were tested in vitro for their capacity to capture, process, and present the ovalbumin antigen to naive CD4+ T cells. In vivo priming of ovalbumin-specific T cells adoptively transferred to BALB/c mice was analyzed by cytofluorometry in cervical lymph nodes after sublingual administration of mucoadhesive ovalbumin. Results: Three subsets of oral DCs with a distinct tissue distribution were identified: (1) a minor subset of CD207(+) Langerhans cells located in the mucosa itself, (2) a major subpopulation of CD11b(+)CD11c(-) and CD11b(+)CD11c(+) myeloid DCs at the mucosal/submucosal interface, and (3) B220(+)120G8(+) plasmacytoid DCs found in submucosal tissues. Purified myeloid and plasmacytoid oral DCs capture and process the antigen efficiently and are programmed to elicit IFN-gamma and/or IL-10 production together with a suppressive function in naive CD4+ T cells. Targeting the ovalbumin antigen to oral DCs in vivo by using mucoadhesive particles establishes tolerance in the absence of cell depletion through the stimulation of IFN-gamma and IL-10-producing CD4(+) regulatory T cells in cervical lymph nodes. Conclusion: The oral immune system is composed of various subsets of tolerogenic DCs organized in a compartmentalized manner and programmed to induce T(H)1/regulatory T-cell responses.