3000 genes are induced when dendritic cells encounter live bacteria

Using microarray technologies, it is now possible to analyze the expression of thousands of genes during the activation of immune cells. A recent report by Paola Ricciardi-Castagnoli and co-workers at the University of Milano-Bicocca, Italy demonstrates the usefulness of this approach when addressing how dendritic cells (DCs) respond to live Gram-negative bacteria. Using the D1 DC line (which shows similar maturation in culture to that observed for fresh bone-marrow-derived DCs), they have shown that expression of ≈3000 genes is induced upon incubation with live E. coli. These genes include those involved in cytoskeletal rearrangements, antigen processing, control of migration and apoptosis, and inflammatory responses. Most interestingly, expression of IL-2 was found to be induced rapidly. This did not occur in macrophages and the authors conclude that DCs are involved uniquely in T-cell priming. The usefulness of analysis of global gene expression for immunologists continues to become apparent. Nat. Immunol. (2001) 2, 882–888 LON