Models of infection have provided important insight into the function of dendritic cells (DC) in vivo. Several microbial products induce DC maturation via Toll-like receptors, a process that is crucial for the ability of DC to initiate adaptive immune responses. Splenic DC have also been shown to produce IL-12 during infection in vivo. This DC-derived IL-12 might be important to skew T cell responses towards Th1. Microbial infections also induce changes in the DC populations of lymphoid organs, often in a subset-specific manner, manifested as an accumulation and redistribution of DC. Furthermore, data are emerging pointing at an absolute requirement of DC in priming of naïve T cells in vivo.