RNAseq of conventional dendritic cells generated from mouse bone marrow cultures under different conditions
Type 1 conventional dendritic cells (cDC1s) are infrequent immune cells with an essential role in orchestrating immune responses to malignancies or infections. Despite their significance in regulating adaptive immunity, the absence of efficient manufacturing techniques to produce adequate yields of cDC1s has hindered their application in therapeutic settings. Here, we find that Interleukin-4 (IL-4) enhances the yield of cDC1 cells produced from Flt3 ligand (Flt3L) cultures of hematopoietic progenitors from either mice or humans, while inhibiting the generation of plasmacytoid DCs. IL-4 acted predominantly on DC progenitors and its activity relied on the cell intrinsic expression of IL4-RA or STAT6. Both in vitro and in vivo, cDC1s that had been stimulated by IL-4 were effective in activating and promoting the expansion of cytotoxic CD8 T cells. Gene expression analysis pointed to a critical role for IL-4 in promoting cDC1 proliferation in vitro. Overall, our research reveals an unanticipated role for IL-4 in fostering the development and manufacture of bona-fide cDC1s, making it easier to employ them for further mechanistic studies, and opening the door to leveraging their potential use in human diseases. Overall design: RNA-seq profiling of sorted cDC1 and cDC2s generated from mouse bone marrow cultures with different conditions:  Flt3L, Flt3L + IL-4, Flt3L + IL-4+ OP9, Flt3L + OP9, Flt3L + IL-4 + OP9DL-1, and Flt3L + OP9DL-1. Three biological replicates per group except the cDC2 Flt3L + IL-4 + OP9DL-1 group, which has two replicates. Samples were sequenced with an Illumina NextSeq 500 sequencing system, producing between 18-93 million single end 86 bp reads per sample.