Antiviral Innate Immunity: Introduction

The concept of “innate immunity” includes all sorts of measures that exclude, inhibit, or slow down infections with little specificity and without much adaptation or generation of a long-lasting memory. The mammalian innate immune defenses described in this article comprise defensins, the complement system, nonspecific phagocytic and cytolytic leukocytes, and cytokines such as the antivirally active interferons. Since the type I (IFN-α/β) and type III interferon (IFN-λ) systems are our primary defense against viral infections, special attention will be paid to the virus-triggered induction of IFN transcription, the signaling activated by IFNs, and the antiviral factors expressed as a consequence.