Cytokines and host defense in pneumonia

In pneumonia the initiation, maintenance, and resolution of inflammation is dependent upon the complex network of pro-inflammatory and anti- inflammatory cytokines. Much of our knowledge of the role of cytokines in the pathogenesis of pneumonia is derived from animal studies on experimental pneumonia. In contrast to systemic infection, where excessive production of pro-inflammatory cytokines is detrimental, causing organ failure and death, local production of pro-inflammatory cytokines is necessary for host defense against the invasive pathogen. Conversely, the anti-inflammatory cytokine IL- 10 impairs host defense in local infections like pneumonia, while it protects against excessive immune activation, like sepsis. Studies on the role of cytokines in pneumonia in humans and animals are discussed in detail.