CD103+CD11b− salivary gland dendritic cells have antigen cross-presenting capacity

Abstract

Dendritic cells (DCs) in lymphoid and non-lymphoid tissues are professional antigen-presenting cells that are essential for effective immunity and tolerance. However, the presence and characteristics of DCs in steady-state salivary glands (SGs) currently remain unknown. We herein identified CD64−CD11c+ classical DCs (cDCs) as well as CD64+ macrophages among CD45+MHC class II+ antigen-presenting cells in steady-state murine SGs. SG cDCs were divided into CD103+CD11b− and CD103−CD11b+ cDCs. CD103+CD11b− cDCs expressed XCR1, CLEC9A, and interferon regulatory factor 8, whereas CD103−CD11b+ cDCs strongly expressed CD172a. Both cDC subsets in SGs markedly expanded in response to the Flt3 ligand (Flt3L), were replenished by bone marrow-derived precursors, and differentiated from common DC precursors, but not monocytes. Furthermore, ovalbumin-pulsed SG CD103+CD11b− cDCs induced the proliferation of naïve ovalbumin-specific CD8+ T cells and production of interferon-γ from proliferating T cells. SG CD103+CD11b− cDCs expanded by Flt3L in vivo exhibited the same properties. These results indicate that bona fide cDCs reside in steady-state murine SGs and cDCs with the CD103+CD11b− phenotype possess antigen cross-presenting capacity. Moreover, Flt3L enhances protective immunity by expanding cDCs. Taken together, SG cDCs might play an important role in maintaining immune homeostasis in the tissues.