Selective inhibition of TNF-a or IL-1b does not affect E. coli-induced inflammation in human whole blood

Inhibition of the inappropriate and excessive inflammatory response has been a main issue in sepsis-related research. Historically, TNF-a and IL-1b have been postulated as key mediators in sepsis, but selective inhibition of these cytokines has failed in clinical trials. Recently it was found that inhibition of upstream recognition by complement and CD14 could efficiently reduce Escherichia coli (E. coli)-induced inflammation. An ex vivo model with lepirudin-anticoagulated human whole blood was used to explore the significance of selective inhibition of TNF-a and IL-1b in E. coli-induced inflammation. The effect of TNF-a, IL-1b, complement and CD14 on the inflammatory response was assessed by adding highly specific neutralizing agents to these mediators. Proinflammatory cytokines, expression of CD11b and oxidative burst were measured. The controls included relevant isotype-matched immunoglobulins and peptides. Selective inhibition of TNF-a or IL-1b had no impact on E. coli-induced release of proinflammatory cytokines, CD11b-upregulation or oxidative burst. In contrast, the combined inhibition of complement and CD14 virtually abolished these responses. These data suggest that both TNF-a and IL-1b are downstream mediators and as single mediators play a limited role within the complex inflammatory reactions induced by E. coli.