Early host-pathogen interactions in the liver and spleen during systemic murine listeriosis: an overview

Systemic listeriosis initiated by parenteral inoculation of mice with Liste ria monocytogenes has been used extensively as a model infection for studyi ng mammalian host defense against intracellular bacterial pathogens in gene ral. Most effort has been expended on trying to understand the requirement for specific T cell-mediated immunity for combatting infection with this pa thogen. By contrast, non-specific defenses have received much less attentio n. However, it is now obvious that these early innate defenses are critical ly important for the well-being of the host. If these early defenses fail t o act, the murine host is rendered exquisitely susceptible to L. monocytoge nes, and rapidly succumbs to overwhelming infection before T cell-mediated immunity can be generated and expressed. The most critical of these early d efenses is mediated by neutrophils that rapidly accumulate in large numbers at foci of Listeria infection in the liver and spleen. These neutrophils a ct to curtail the growth of L. monocytogenes to levels that subsequently ca n be dealt with by: specific defenses that are recruited into infectious fo ci later. In the absence of this neutrophil-mediated defense, an otherwise sublethal inoculum of L. monocytogenes rapidly grows to lethal numbers. An overview of this early aspect of murine listeriosis is presented below.