DC hematopoiesis and subsets. (A) All identified DC subsets can be generated from either a common myeloid progenitor (CMP) or common lymphoid progenitor (CLP) depending on the cytokines and growth factors present. DCs can be broadly categorized as cDCs or precursor DCs. pDCs are understood to be a subset of precursor DCs that have plasma cell morphology, an immature phenotype, and secrete type I IFN after activation. Monocyte-derived DCs or “inflammatory DCs” are similar to cDCs in form and function and correlate with in vitro GM-CSF-generated DCs. cDCs can be categorized as lymphoid tissue resident and migratory DCs. DCs were categorized previously as lymphoid or myeloid (mDCs) based on the hypothesis that each had separate progenitors, a convention that has persisted in the experimental and clinical evaluation of DC subsets. Professional illustration by Alice Y. Chen. (B) In mice, pDCs are identified as CD11c^loCD11b⁻ Siglec-H⁺PDCA-1⁺, whereas in humans, they are lin⁻MHC II⁺CD11c⁻CD123(IL-3Rα)⁺BDCA2(CD303)⁺. Mouse mDCs are identified as CD11c⁺CD11b⁺B220⁻ (CD45R⁻) NK1.1⁻, whereas human mDCs are lin⁻ MHCII⁺CD11c⁺CD123⁻BDCA1(CD1b/c)⁺. Other phenotypic differences between mouse and human DC precursors are also listed in the table. HSC indicates hematopoietic stem cells; MPP, multipotent progenitor; CMP, common myeloid progenitor; CLP, common lymphoid progenitor; pDC, plasmacytoid DC; mDC, myeloid DC; LN, lymph node; and LP, lamina propria.