Phagocytic System

Abstract Phagocytes were initially thought to be harmful to the host, contributing to the untoward consequences of infection and inflammation. In 1898, Metchnikoff first suggested that “the essential and primary element in typical inflammation consists in a reaction of the phagocyte against a harmful agent.”After establishing that phagocytes were helpful in defense against bacteria, Metchnikoff predicted that defects in phagocyte function might predispose the host to increased numbers and severity of infections due to microorganisms. Patients with decreased phagocyte counts or with phagocyte functional defects do, in fact, have recurrent or even fatal infections as well as impaired wound healing. Moreover, evidence has also accumulated demonstrating that aberrant phagocyte activation can contribute to untoward complications of inflammation. Functional defects in phagocytes can lead to recurrent cutaneous abscesses, periodontitis, paronychia, pneumonitis, osteomyelitis, and occasionally life-threatening sepsis.