Sequential lymphotoxin-β receptor and retinoic acid receptor signals regulate cDC2 fate

Type 2 conventional dendritic cells (cDC2s) are functionally and phenotypically heterogenous. Previous work in mice and humans identified two cDC2 subsets (cDC2As and cDC2Bs) and a monocytic DC3 subset. However, the microenvironmental cues governing their distinct differentiation pathways remain unclear. Here, we delineate mouse cDC2 lineage relationships and the sequential signals required for cDC2A maintenance. We show that cDC2s, arising from the CLEC9A⁺ cDC progenitor, encompass T-BET-expressing cDC2As and two cDC2B subsets distinguished by MGL2 expression, with monocytic DC3s exhibiting transcriptional overlap with Mgl2^- cDC2Bs. Among these subsets, T-BET⁺ cDC2As dominate the spleen where they require cell-intrinsic retinoic acid signaling to sustain their differentiation via Notch signals. Lymphotoxin-β receptor signaling on splenic cDC2s limits F-actin content retaining cDC2s at sites of retinol delivery. In summary, these data establish the developmental and transcriptional relationships between diverse cDC2 subsets and identify signals that regulate their prevalence in specific lymphoid tissues.