SummaryDendritic cell (DC)-mediated cross-presentation of exogenous antigens acquired in the periphery is critical for the initiation of CD8+ T cell responses. Several DC subsets are described in human tissues but migratory cross-presenting DCs have not been isolated, despite their potential importance in immunity to pathogens, vaccines, and tumors and tolerance to self. Here, we identified a CD141hi DC present in human interstitial dermis, liver, and lung that was distinct from the majority of CD1c+ and CD14+ tissue DCs and superior at cross-presenting soluble antigens. Cutaneous CD141hi DCs were closely related to blood CD141+ DCs, and migratory counterparts were found among skin-draining lymph node DCs. Comparative transcriptomic analysis with mouse showed tissue DC subsets to be conserved between species and permitted close alignment of human and mouse DC subsets. These studies inform the rational design of targeted immunotherapies and facilitate translation of mouse functional DC biology to the human setting.

Human dendritic cells (DCs) regulate the balance between immunity and tolerance through selective activation by environmental and pathogen-derived triggers. To characterize the rapid changes that occur during this process, we analyzed the underlying metabolic activity across a spectrum of functional DC activation states, from immunogenic to tolerogenic. We found that in contrast to the pronounced proinflammatory program of mature DCs, tolerogenic DCs displayed a markedly augmented catabolic pathway, related to oxidative phosphorylation, fatty acid metabolism, and glycolysis. Functionally, tolerogenic DCs demonstrated the highest mitochondrial oxidative activity, production of reactive oxygen species, superoxide, and increased spare respiratory capacity. Furthermore, assembled, electron transport chain complexes were significantly more abundant in tolerogenic DCs. At the level of glycolysis, tolerogenic and mature DCs showed similar glycolytic rates, but glycolytic capacity and reserve were more pronounced in tolerogenic DCs. The enhanced glycolytic reserve and respiratory capacity observed in these DCs were reflected in a higher metabolic plasticity to maintain intracellular ATP content. Interestingly, tolerogenic and mature DCs manifested substantially different expression of proteins involved in the fatty acid oxidation (FAO) pathway, and FAO activity was significantly higher in tolerogenic DCs. Inhibition of FAO prevented the function of tolerogenic DCs and partially restored T cell stimulatory capacity, demonstrating their dependence on this pathway. Overall, tolerogenic DCs show metabolic signatures of increased oxidative phosphorylation programing, a shift in redox state, and high plasticity for metabolic adaptation. These observations point to a mechanism for rapid genome-wide reprograming by modulation of underlying cellular metabolism during DC differentiation.