Host defences of invertebrates to pathogens and parasites

Abstract

Textbooks on immunology rarely spend more than a few pages describing the principles of invertebrate immunology. Coming away from these often gives the reader the impression that this immune system is simple and non-specific in nature yet with over 1.3 million extant species of invertebrates, there is inevitably a great diversity of strategies to defend against disease. Furthermore, invertebrates have unique mechanisms of defence including the prophenoloxidase system only found in arthropods, molluscs, echinoderms and tunicates and some forms of ‘acquired’ immunity where the host has an apparent specific heightened response on second exposure to a parasite or pathogen. This chapter aims to provide a concise overview of the broad invertebrate defence mechanisms to parasites and pathogens, and how such agents can overcome and/or circumvent these defences to cause disease.