Drosophila: a model for the understanding of innate immunity

Drosophila as other insects are particularly resistant to microbial infecti on. Drosophila host defense system relies on several innate reactions: imme diate activation of two proteolytic cascades leading to blood clotting and to melanization, phagocytosis and encapsulation of intruders by bloods cell s, induced synthesis by the fat body of a battery of antimicrobial peptides which are secreted into the hemolymph. Recent genetic analysis has reveale d striking similarities between signaling pathways leading to antimicrobial peptide gene expression in Drosophila and cytokine-induced expression of t he genes coding for acute phase proteins in mammals. The finding that insec t and mammalian immunity involve related signaling pathways offers the prom ise that genetic studies in Drosophila might contribute to our understandin g of the innate immune response in higher organisms.