How Protozoa Evade Intracellular Killing

Excerpt

Once swept inside a polymorphonuclear or mononuclear leukocyte and enclosed within a phagocytic vacuole, ingested microorganisms are immediately confronted with a toxic array of both oxygen-dependent and oxygen-independent microbicidal mechanisms. Phagocytosis not only triggers the generation of lethal oxygen intermediates, including superoxide anion (O-²), hydrogen peroxide (H²O²), and hydroxyl radical, but also stimulates cytoplasmic granules and lysosomes to fuse with the pathogen-containing vacuole and discharge their potentially destructive components. In most instances, these mechanisms act swiftly, and intracellular microbial death within this churning milieu is the rule. Certain pathogens, however, escape intravacuolar killing, and successfully convert phagocytic cells into benign