Figure 1.

The origin and development of pulmonary dendritic cells (DCs) from hematopoietic stem cells (HSCs). In the bone marrow, HSCs give rise to common myeloid progenitors (CMPs), which differentiate into more restricted macrophage and DC progenitors (MDPs). MDPs give rise to common DC progenitors (CDPs), then to precursor DCs (pre-DCs) and plasmacytoid DCs (pDCs). Alternatively, MDPs can give rise to common monocyte progenitors, which then differentiate into monocytes in circulation. The pre-DCs, pDCs, and monocytes then leave the bone marrow and travel via the blood to secondary lymphoid organs and nonlymphoid tissues. After migrating into the lung, pre-DCs differentiate into CD103⁺ DC and CD11b⁺ DC subsets. Monocytes are recruited to the lungs under inflammatory stimuli and further differentiate into monocyte-derived DCs (monoDCs).