Cellular and humoral immune interactions between Drosophila and its parasitoids.

The immune interactions occurring between parasitoids and their host insects, especially in Drosophila-wasp models, have long been the research focus of insect immunology and parasitology. Parasitoid infestation in Drosophila is counteracted by its multiple natural immune defense systems, which include cellular and humoral immunity. Occurring in the hemocoel, cellular immune responses involve the proliferation, differentiation, migration and spreading of host hemocytes and parasitoid encapsulation by them. Contrastingly, humoral immune responses rely more heavily on melanization and on the Toll, Imd and Jak/Stat immune pathways associated with antimicrobial peptides along with stress factors. On the wasps' side, successful development is achieved by introducing various virulence factors to counteract immune responses of Drosophila. Some or all of these factors manipulate the host's immunity for successful parasitism. Here we review current knowledge of the cellular and humoral immune interactions between Drosophila and its parasitoids, focusing on the defense mechanisms used by Drosophila and the strategies evolved by parasitic wasps to outwit it.