Transcription factors TCF4 and KLF4 respectively control the development of the DC2A and DC2B lineages

Conventional dendritic cells (cDCs) are a heterogeneous population of professional antigen-presenting cells that bridge innate and adaptive immunity. Many studies in mice have identified various populations of cDCs whose inter-relationships and discrete identities, as well as their link to plasmacytoid DCs (pDCs), have not been cohesively addressed. Here, by combining single-cell sequencing, transcription factor fate-mapping models, conditional knockout models and adoptive transfer, we show that Klf4 expression clearly separates cDC lineage from the pDC lineage, and defined two pre-DC2 subsets: Siglec-H⁺CD115^- pre-DC2s and Siglec-H^loCD115⁺ pre-DC2s. While Siglec-H⁺CD115^- pre-DC2s represent the pDC-like cells that give rise to CD7⁺CD11b^lo DC2As in a TCF4-dependent manner, Siglec-H^loCD115⁺ pre-DC2s give rise to CD7^-CD11b^hi DC2Bs in a KLF4-dependent manner. These data reveal the transcriptional basis of two pre-DC2 subsets and present a firm framework for mouse cDC classification, paving the way for a better understanding of these cells in tissues and in disease.