Innate immunity and its evasion and suppression by hymenopteran endoparasitoids

Recent studies suggest that insects use pattern recognition molecules to di stinguish prokaryotic pathogens and fungi from "self" structures. Less unde rstood is how the innate immune system of insects recognizes endoparasitic Hymenoptera and other eukaryotic invaders as foreign. Here we discuss candi date recognition factors and the strategies used by parasitoids to overcome host defense responses. We suggest that host-parasitoid systems are import ant experimental models for studying how the innate immune system of insect s recognizes foreign invaders that are phylogenetically more closely relate d to their hosts. The strategies used by parasitoids suggest that insects m ay employ "hidden-self" recognition molecules for attacking foreign objects intruding the open circulatory system. (C) 2001 John Wiley & Sons, Inc.