Characterization of resident and migratory dendritic cells in human lymph nodes

Dendritic cells (DCs) initiate adaptive immune responses in lymph nodes (LNs). In mice, LN DCs can be divided into resident and tissue-derived populations, the latter of which migrate from the peripheral tissues. In humans, different subsets of DCs have been identified in the blood, spleen, and skin, but less is known about populations of resident and migratory tissue-derived DCs in LNs. We have analyzed DCs in human LNs and identified two populations of resident DCs that are present in all LNs analyzed, as well as in the spleen and tonsil, and correspond to the two known blood DC subtypes. We also identify three main populations of skin-derived migratory DCs that are present only in skin-draining LNs and correspond to the DC subsets found in the skin. Resident DCs subsets induce both Th1 and Th2 cytokines in naive allogeneic T lymphocytes, whereas the corresponding blood subsets failed to induce efficient Th2 polarization. LN-resident DCs also cross-present antigen without in vitro activation, whereas blood DCs fail to do so. Among migratory DCs, one subset was poor at both CD4+ and CD8+ T cell activation, whereas the other subsets induced only Th2 polarization. We conclude that in humans, skin-draining LNs host both resident and migratory DC subsets with distinct functional abilities.