Bali Pulendran, PhD has worked in the fields of cellular and molecular immunology for nearly 20 years. During his Ph.D under Professor Gus Nossal, he identified a novel mechanism of immunological tolerance in germinal center B cells. Subsequently, as a post doctoral fellow at Immunex, and later as a junior faculty at the Baylor Institute for Immunology Research, he studied dendritic cells (DCs) and made the observations that distinct subsets of DCs differentially stimulate distinct classes of T-helper responses, and that Flt3-Ligand was a growth factor for multiple DC subsets in vivo, in mice and in humans. Since then, his work has focused on understanding the mechanisms by which the innate immune system regulates the adaptive immune response, and how these can be harnessed in vaccine development. Some key observations to result from this work include: (i) the demonstration that signaling via different Toll like receptors differentially regulate the class of the immune response, (ii) identification of signaling pathways that program DCs to induce Th2 and tolerogenic responses, (iii) identification of subsets of DCs and macrophages that regulate tolerogenic responses in the intestine, (iv) novel mechanistic insights into the molecular mechanisms of type I IFN induction in plasmacytoid DCs, (v) application of systems biological tools to predicting the immunogenicity of vaccines in humans, and the application of this approach to gaining new biological insights into the mechanism of action of vaccines.