A Toll pathway effector protects Drosophila specifically from distinct toxins secreted by a fungus or a bacterium

Major immune response pathways control the expression of hundreds of genes that represent potential effectors of the immune response. The Drosophila Toll pathway is required in the host defenses against several Gram-positive bacterial infections as well as against fungal infections. The current paradigm is that peptides secreted in the hemolymph during the systemic immune response are either bona fide antimicrobial peptides or likely ones. The finding of a dual role for one Toll pathway effector in the resilience to both Enterococcus faecalis and Metarhizium robertsii infections underscores an original concept in insect innate immunity. Evolution can select effectors tailored to protect the host from the action of microbial toxins of prokaryotic or eukaryotic origin, independently of antibodies or detoxification pathways.