Bacterial virulence and the inflammatory system.

The sequence of events by which bacteria activate immune responses is extremely complex. The culmination of these events often leads to immunopathologic consequences, which are evident in both local and systemic bacterial infections. Where mediators are generated, immune/inflammatory cells are activated, and tissue is destroyed. In the case of acute inflammatory reactions, the following scenario can occur: bacteria activate the complement cascade, polymorphonuclear leukocytes are recruited, and lysosomal enzymes and toxic oxygen products that destroy both the inciting bacteria and the surrounding tissue are generated. The complex interplay among the various mediator systems, inflammatory cells, and toxic products is recognized as a complicated array of pathways necessary for clearance of a given bacterial infection. Understanding these pathways, which ultimately lead to an appropriate immune response to the bacteria, is an extremely challenging problem to microbiologists and immunologists alike.