|Institution:||Washington University in St. Louis|
|Keywords:||Dendritic cell; Development; Hematopoiesis; Host-Pathogen; Immunity; Macrophage; Biology|
|Full text PDF:||http://openscholarship.wustl.edu/art_sci_etds/67|
Classical dendritic cells (cDCs) are essential initiators of innate and adaptive immune responses to pathogens. However, study of these critical cells has been complicated by their similarity to other hematopoietic lineages by cell surface markers. We identified Zbtb46 as a transcription factor selectively expressed by cDCs and their committed progenitors, but not by plasmacytoid DCs (pDCs), monocytes, macrophages or other related myeloid lineages. Using homologous recombination, we replaced the first coding exon of Zbtb46 with GFP to inactivate the locus while allowing detection of Zbtb46 expression. GFP expression in Zbtb46gfp mice recapitulated the cDC-specific expression of the native locus, being restricted to cDC precursors and lymphoid-organ and tissue-resident cDCs. Although cDCs developed in Zbtb46gfp/gfp (Zbtb46-deficient) mice, they maintained expression of granulocyte colony-stimulating factor and leukemia inhibitory factor receptors, which are normally down-regulated in order to restrict cDC responsiveness to non-cDC growth factors. Importantly, Zbtb46gfp mice in combination with mice expressing the diphtheria toxin receptor (DTR) under the control of the Zbtb46 locus allowed for specific visualization and depletion of cDCs in vivo. A further complication in the analysis of cDC function in vivo is the developmental specialization of distinct cDC subsets. Previous work in our lab generated mice deficient in the transcription factor BATF3, which resulted in the specific loss of CD8+ cDCs. Batf3-/- mice were unable to survive infection with the parasite Toxoplasma gondii or reject immunogenic tumors. In contrast, the role of the complementary CD11b+ cDC subset remains unclear. We identified Notch2 as a critical regulator of CD11b+ cDC differentiation; mice deficient in Notch2 in myeloid cells specifically lacked this population in vivo. In combination with Zbtb46DTR mice, we determined that Zbtb46+ Notch2-dependent cDCs were specifically required for survival after infection with the enterohemorrhagic bacterium Citrobacter rodentium. Following infection, CD11b+ cDCs were required for the induction of anti-microbial peptides from epithelial cells. Collectively, our studies have clarified the identity of the cDC lineage and provided the first demonstration of a non-redundant function of CD11b+ cDCs in response to pathogens in vivo. In humans, manipulation of this cDC subset may be useful for enhancing immunity to related enterohemorrhagic pathogens.