Dendritic cells are antigen-presenting cells that play a critical role in linking the innate and the adaptive immune systems. In the September issue of Nature Immunology, Francesca Granucci and colleagues at the University of Milano-Bicocca, Italy, report the results of an oligonucleotide microarray screen to identify genes regulated in dendritic cells following activation by Gram-negative bacteria (Nature Immunology 2001, 2:882-888). They analysed the transcriptome of the dendritic cell-line D1 at several time points after activation with bacteria. Their analysis identified changes in a large number of genes, including genes implicated in inflammation, apoptosis, signal transduction and transcription. Also, Granucci et al. observed an induction of interleukin 2 (IL-2) mRNA at early time points (4-6 hours) and confirmed the importance of dendritic cell-derived IL-2 using bone marrow dendritic-cells from IL-2-/- knockout mice. These results provide a molecular clue to explain the priming of naive T cells by dendritic cells during the immune response.