Progenitors of distinct lineages shape the diversity of mature type 2 conventional dendritic cells.

Conventional Dendritic Cells (cDC) are antigen-presenting cells comprising cDC1 and cDC2 subsets, responsible for priming naïve CD8+ and CD4+ T cells, respectively. Recent studies have unveiled cDC2 heterogeneity and identified various cDC2 progenitors beyond the common DC progenitor (CDP), hinting at distinct cDC2 lineages. By generating Cd300ciCre-hCD2R26tdTomato reporter mice, we identified a bone marrow pro-cDC2 progenitor exclusively generating cDC2 in vitro and in vivo. Single-cell analyses and multiparametric flow cytometry demonstrated that pro-cDC2 encompass myeloid-derived pre-cDC2 and lymphoid-derived pDC-like precursors differentiating into a transcriptionally convergent cDC2 phenotype. Cd300c-traced cDC2 had distinct transcriptomic profiles, phenotypes, and tissue distributions compared to Ms4a3CreR26tdTomato lineage-traced DC3, a monocyte-DC progenitor-derived subset that bypasses CDP. Mice with reduced Cd300c-traced cDC2 showed impaired humoral responses to a blood-borne antigen. We conclude that progenitors of distinct lineages shape the diversity of mature cDC2 cells across tissues. Thus, ontogenesis may impact tissue immune responses. Overall design: We performed single-cell RNA/ATAC (multiome) sequencing on Lin- B220- Flt3+ BM progenitor cells extracted from three CD300c-iCre-hCD2 R26tdTomato mice.