Natural resistance to infection: leukocyte functions

The nonspecific immune system has an extraordinarily important role in prevention of and response to wound infection. In the presence of injury or contamination, leukocytes adhere to local endothelial cells in response to complement signals through an integrin mechanism; they then migrate to the affected tissue site to locate, ingest, and kill microbes. Clinically, the major weaknesses in this system are impairment of cell recruitment and depression of microbial killing mechanisms; intracellular killing is the most problematic step in the process. Provided that leukocytes are able to migrate and ingest bacteria, nonoxidative killing proceeds in a normal fashion. Oxidative killing, however, can be profoundly impaired by poor blood perfusion and oxygenation. Low oxygen tension is a common clinical problem in surgical sites and wounds. There are a number of ways in which oxidative killing can be supported and facilitated in the clinical arena in a manner that is likely to enhance the effects of antibiotics in the treatment and prevention of infection.