Host-pathogen interactions in drosophila: new tricks from an old friend

Insects rely solely on innate immune responses to combat a wide array of pathogens. With its powerful genetics, drosophila has proven especially powerful for the study of humoral innate immunity, characterized by the rapid induction of antimicrobial peptides. The two signaling pathways involved, Toll and Imd, have been studied intensely, but other aspects of the drosophila immune response are less well understood. A flurry of reports has focused on the mechanisms of phagocytosis, antiviral immunity and viral pathogenesis in drosophila. These studies have taken advantage of genome- wide RNA-mediated interference screening in drosophila cells, as well as more traditional genetic tools available in the fly. This review discusses advances in these exciting new areas of drosophila immunity.