ABSTRACT
Innate immunity is a phylogenetically ancient defense system that provides a rst barrier against a broad range of pathogens through nonspecic defense mechanisms. In the absence of immune defense, a single bacterium replicating every 60 min could have, within 3 days, a theoretical progeny of approximately 272 (i.e., more than 1021 bacteria). The innate, nonadaptive immune defense of the host has a formidable task to keep the multiplication and the spread of pathogens under control until a specic adaptive immune response has developed. Here, we outline the numerous lines of innate immediate defense mechanisms that protect hosts from infection with the facultative intracellular bacterium Listeria monocytogenes (Figure 13.1).
