[Diagnosis of sepsis based on the host response]

Sepsis is often a fatal condition, and excessive production of host inflammatory mediators including cytokines, are considered to be responsible for its lethality. We investigated the biology of TNF-alpha, IL-1, IL-6, and IL-10 with particular emphasis on its role in murine gut-derived sepsis due to Pseudomonas aeruginosa and found that these cytokine levels in serum showed significant increases at lethal conditions. Furthermore, we studied the cytokine levels in serum and BALF of mice after pulmonary infection with Klebsiella pneumoniae. The results showed that inflammatory cytokines in BALF demonstrated high levels at the early stage of infection in response to local inflammation of the lung. On the other hand, cytokine levels in serum abruptly increased at the late stage of infection in response to systemic inflammation. These results revealed that it is important to discriminate between systemic inflammation and local inflammation to diagnose sepsis.