A novel culture system to efficiently generate the equivalent of peripheral tissue CD103⁺ cDCs from mouse bone marrow. (A) Four major DC subsets are recognized in vivo. In the steady state, plasmacytoid DCs (pDCs), CD11b⁺ conventional DC (cDCs) and CD8α⁺/CD103⁺ cDCs are present in lymphoid and peripheral tissues, whereas monocyte-derived DC (moDCs) are almost exclusively found in the periphery. (B) Two culture systems that are widely used to generate DC subsets from mouse bone marrow. Culture in GM-CSF produces monocyte-derived DCs. Cultures based on FLT3L yield 3 subsets: pDCs, CD11b⁺ cDCs, and an equivalent of the CD8α⁺/CD103⁺ cDC lineage. A drawback of this system is the limited overlap in surface markers between CD8α⁺/CD103⁺ cDCs and their in vitro equivalent. These cDCs are identified based on CD24 expression but do not express CD8α and express only very limited CD103. (C) In this issue of Blood, Mayer et al show a novel method to generate in vitro CD103⁺ cDCs. By 16 days of culture in the presence of FLT3L and GM-CSF, a 90% pure population of CD103⁺ Clec9A⁺ cDCs can be obtained. These cells resemble the in vivo peripheral CD103⁺ cDC subset based on phenotypic markers, transcription factor dependency, gene expression profile, and functional abilities.