Immune functions in crustaceans: lessons from flies

In recent years insects, notably Drosophila, have emerged as a popular model for studying immune responses to bacterial and fungal pathogens. Due to the availability of the complete genome sequence, genome-wide scans of immune responses have been performed using microarray analyses. These analyses have revealed the presence of two major pathways: Toll and Imd. Each pathway consists of four steps: (i) recognition through pattern recognition receptors; (ii) modulation by serine proteases; (iii) signal transduction leading to translocation of transcription factors and (iv) humoral and cellular responses. We have compared the information from insects with those currently available in crustaceans, and have identified commonalities and differences. Remarkably, in both insects and crustaceans, little is known about their anti-viral responses. Future research will have to focus on these anti-viral immune responses ultimately to control viral diseases, which are at present a major threat to culturing penaeid shrimp.