1 - Insect and Vertebrate Immunity: Key Similarities versus Differences

Abstract

This chapter uses a comparison between insect and higher vertebrate immune reactions to highlight some of the progress that has been made in the understanding of how innate immune recognition has evolved to protect multicellular organisms against potentially damaging organisms. The similarities between mammals and nonmammals are more than one that is reflected in their sensing mechanisms, which affects recognition of pathogen-associated molecular structures. The binding properties of antibodies, enabling the variable binding domains to attach to almost any molecular structure (antigens) and the ontogenic elimination process of self-binding antibodies by clonal selection, allow higher vertebrates with adaptive immune systems to signal nonself structures. The similarities are also evident in extracellular sensor particles, recognition of self, and recognition of altered-self. The differences between insect and vertebrate immunity are evident in acquired (adaptive) immune system in higher vertebrates and immunological memory, involving clonally selected antibody-producing cells and inducible tolerance and memory in invertebrates. One of the questions associated with immune induction and protection is the size of the fitness cost imposed on the insect, which is difficult to explain by the induction of immune proteins alone. However, the recent observation that lipid particles are procoagulants and involved in defense and detoxification reactions could indicate immune-related post-translational modifications of lipid particles that affect lipid transport and metabolism. The most unexpected outcome of experimental studies involving the induction of the immune defense is that the elevated immune status can be transmitted to subsequent generations. Whatever the mechanism, the implications are that insects are able to acquire tolerance to damaging objects or substances by an incremental increase of an induced immune status in subsequent generations.