Humoral immunity in insects: Antimicrobial peptides and other host defense peptides

Abstract

The discovery of antimicrobial peptides in insects in the 1980s helped lay the foundation for the field of humoral innate immunity in animals. These molecules were first identified owing to their microbe-killing activity, promising novel strategies for development of antibiotics and therapeutics. Today, they remain an integral part of the study of insect immune systems as readouts of immune activation. This chapter provides a modern synthesis of peptide structures and activities, and details a new appreciation for the roles these peptides have in host-microbe interactions and immune system evolution. Recent work has further suggested roles for these small proteins beyond combatting infection, and so we endorse increased use of the term “host defense peptides” as a mechanism-agnostic descriptor in such cases. We close by highlighting unanswered questions in insect immunology where antimicrobial and host defense peptides will play important roles.