The thesis explores the impact of the transcription factor IRF4 on the differentiation of mouse embryonic stem cells (ESCs) into myeloid dendritic cell (DC) progenitors. For this study, I used two chemically inducible ESC clones carrying the IRF4 transgene. This investigation explores the role of IRF4 in regulating this developmental process. Through flow cytometry analysis and gene expression profiling, it was observed that enforced expression of IRF4 led to a decreased percentage of CD45+ and CD34+ cells, indicative of suppression in ESC-derived myeloid blood cell development. Additionally, the results from RT-PCR analyzes revealed an increased expression of IRF4 when the cells were induced by doxycycline both at their undifferentiated stage and during the differentiation process. Together these results suggest that IRF4 suppresses ESC-derived myeloid blood cell development and exerts a general inhibitory effect on ES-DC development.