Immunity can be defined as the ability of each living organism is Maintain its own integrity ( homeostasis ) through Recognizing the non -self and discriminating it from the self . In vertebrates innate and adaptive immunity mechanisms are Involved in fighting against Pathogens . According this general opinions , filogenetically older invertebrates respond this infection activating innate immunity reactions only . How- ever , a growing line of evidence indicates the immune system That in insects , crustaceans and molluscs can recognize and remember Specifically infection with Certain Pathogens . Involvement of multiple isoforms of pattern recognition receptors containing variable Ig domains , eg . Dscam insect and snail FREPs is implicated in specific recognition of different Pathogens and in selection of Immune Competent fagocytes . There are suggestions That invertebrates possess an alternative type of adaptive immunity through mechanisms Functioning Which differ from the ones known in vertebrates . The review Describes new discoveries in invertebrate immunity , with special focus on insects.