Although all dendritic cells (DCs) are capable of pathogen recognition and antigen presentation, they are a heterogeneous cell population in terms of locations, phenotypes, and immunological functions. This plasticity allows DCs to differentially shape the immune response when presented with diverse pathogens. Most of our knowledge about different DC subsets has come from studies in mouse where several lymphoid tissue-resident and migratory DC subsets have been characterized. Mouse DC subsets include CD8 alpha+ and CD11b+ lymphoid tissue-resident classical DCs (cDCs), CD103+CD11b-, CD103+CD11b+, and CD103-CD11b+ nonlymphoid tissue-resident/migratory cDCs, plasmacytoid DCs, Langerhans cells, and inflammatory monocyte-derived DCs (MoDCs). Significant differences in some of the primary cell surface markers expressed by mouse and human DCs has complicated the characterization of human DC subsets. To date, two subsets of human cDCs, CD141/BDCA3+ cDCs and CD1c/BDCA1+ cDCs, have been found in the blood, spleen, and tonsils and are thought to correspond to mouse lymphoid tissue-resident CD8 alpha+ cDCs and CD11b+ cDCs, respectively. Human CD1c/BDCA1+ DCs are the major cDC subset found in blood, while CD141/BDCA3+ cDCs are relatively rare. Additional human DC subsets that have been characterized include human plasmacytoid DCs, which are present in blood and lymphoid tissue, as well as two types of human dermal DCs, CD1a+CD14- DCs and CD1a-CD14+ DCs and Langerhans cells.