Molecular genetics of Drosophila immunity.

Insects resist bacterial infections through the induction of both cellular and humoral immune responses. The cellular response involves the mobilization of hemocytes, whereas the humoral response utilizes antibacterial peptides that are synthesized in the fat bodies and secreted into the circulating hemolymph. Recent studies suggest that the induction of the humoral response involves Rel-containing regulatory proteins, Dif and dorsal, which are related to mammalian NF-kappa B. These regulatory proteins function as sequence-specific transcription factors that induce the expression of immunity genes, including cecropin and diptericin. In mammals, NF-kappa B has been implicated in both lymphocyte differentiation and the acute-phase response. The finding that insect and mammalian immunity involve related transcription factors offers the promise that genetic studies in Drosophila might lead to the identification of novel components mediating mammalian immunity.