Activation of an innate immune response in large numbers of permeabilized Drosophila embryos.

Innate immunity in Drosophila involves the inducible expression and synthesis of antimicrobial peptides. We have previously shown that not only Drosophila larvae and adults, but also embryos, are capable of mounting an immune response after injection of bacterial substances. To simplify genetic dissection of the signaling pathways involved in immune-gene regulation we developed a procedure for permeabilization of large number of embryos and subsequent infiltration with bacterial fragments. This approach, which promoted expression of CecropinA1- and Diptericin-driven β-gal expression in the epidermis of more than 90% of the treated embryos, will enable analysis of mutants that are embryonic lethal. Thus, genes that are involved in essential pleiotrophic functions, in addition to being candidates in immune-regulation will be amenable for analysis of their involvement in the fly's immune defense.