Specificity and signaling in the Drosophila immune response

Abstract

The Drosophila immune response is characterized by the rapid and robust production of a battery
of antimicrobial peptides immediately following infection. The genes encoding these antimicrobial
peptides are controlled by two NF-κB signaling pathways that respond to microbial infection. The IMD
pathway is triggered by DAP-type peptidoglycan, from the cell wall of most Gram-negative and certain
Gram-positive bacteria, and activates the NF-κB precursor protein Relish. The Toll pathway, on the
other hand, is stimulated by lysine-type peptidoglycan from many Gram-positive bacteria, β 1,3
glucans from many fungi, as well as by microbial proteases. Toll signaling leads to the activation and
nuclear translocation of DIF or Dorsal, two other NF-κB homologs. This review presents our current
understanding of the molecular mechanisms involved in microbial recognition and signal transduction
in these two innate immune pathways.