Dendritic cells (DCs) are specialized immune cells critical for regulating the innate and adaptive immune responses. While DCs, including conventional DC (cDC) and plasmacytoid DC (pDC) are short-lived and are constantly replenished from their progenitors of myeloid and lymphoid lineages, the study of developmental control of DCs is hampered by limited numbers of the progenitor cells. Here we immortalized hematopoietic stem and progenitor cells (iHSPC) by introducing an inducible Hoxb8 gene into 5-fluorouracil (5FU)-treated mouse bone marrow. The iHSPCs were able to develop into pDC and cDC in response to Flt3 ligand (FLT3L) treatment. Moreover, the iHSPCs were capable of producing T, B, macrophages and granulocytes in addition to DCs when adaptively transferred into γ-irradiated recipient mice, suggesting that the iHSPCs retained their pluripotency for differentiation. We have previously shown that common lymphoid progenitors (CLPs) exhibited higher pDC potential than did cDCs. TLR-induced inflammation or influenza virus infection remodeled the developmental program by promoting cDC formation but inhibiting pDC generation in vitro and in vivo through upregulation of, Id2, a cDC-specific factor and downregulation of Tcf4 and Spib, two pDC-specific factors. Interestingly, the iHSPCs also phenocopied the developmental features of primary CLPs in response to the same stimulation. Lentivirus-mediated RNA silencing in iHSPC had identified STAT3 and AKT as key signaling molecules controlling pDC development from the progenitors. Knockdown of either molecule resulted in increased cDC but reduced pDC potential from iHSPCs. A similar phenotype was observed in conditional knockout of STAT3 in primary progenitor cells. These results have demonstrated that iHSPC is a powerful tool to systemically investigate signaling events dictating DC homeostasis at steady-state and inflammation. Since malfunction or uncontrolled activation of pDCs is associated with autoimmune diseases, such as systemic lupus erythematosis and psoriasis, this study may provide potential therapeutic strategies to circumvent the diseases.