LPS-induced immune response in Drosophila

The study of the regulation of the inducible synthesis of antimicrobial pep tides in Drosophila melanogaster has established this insect as a powerful model in which to study innate immunity. In particular, the molecular chara cterization of the regulatory pathway controlling the antifungal peptide dr osomycin has revealed the importance of Toll receptors in innate immunity. We report here that injection of LPS into flies induces an immune response, suggesting that LPS receptors are used in Drosophila to detect Gram-negati ve bacteria infection. We have identified in the recently sequenced genome of Drosophila eight genes coding for Toll-like;e receptors in addition to T oll, which may function as LPS receptors. However, overexpression of a sele ction of these genes in tissue-culture cells does not result in up-regulati on of the antibacterial peptide genes. These results are discussed in light of the recent data from genetic screens aimed at identifying the genes con trolling the antibacterial response in Drosophila.