The anti-inflammatory effect of combined complement and cd14 inhibition is preserved during escalating bacterial load.

Combined inhibition of complement and CD14 is known to attenuate bacterial-induced inflammation, but the dependency of the bacterial load on this effect is unknown. Thus, we investigated whether the effect of such combined inhibition on Escherichia coli- and Staphylococcus aureus-induced inflammation was preserved during increasing bacterial concentrations. Human whole blood was preincubated with anti-CD14, eculizumab (C5-inhibitor) or compstatin (C3-inhibitor), or combinations thereof. Then heat-inactivated bacteria were added at final concentrations of 5x10(4) -1x10(8) /mL (E. coli) or 5x10(7) -4x10(8) /mL (S. aureus). Inflammatory markers were measured using ELISA, multiplex technology and flow cytometry. Combined inhibition of complement and CD14 significantly (P<0.05) reduced E. coli-induced IL-6 by 40-92% at all bacterial concentrations. IL-1β, IL-8 and MIP-1α were significantly (P<0.05) inhibited by 53-100%, and the effect was lost only at the highest bacterial concentration. TNF and MIP-1β were significantly (P<0.05) reduced by 80-97% at the lowest bacterial concentration. Monocyte and granulocyte CD11b were significantly (P<0.05) reduced by 63-91% at all bacterial doses. Lactoferrin was significantly (P<0.05) attenuated to the level of background activity at the lowest bacterial concentration. For S. aureus similar effects were observed, but the attenuation was in general less pronounced. Compared to E. coli, much higher concentrations of S. aureus were required to induce the same cytokine responses. This study demonstrates generally preserved effects of combined complement and CD14 inhibition on Gram-negative and Gram-positive bacterial-induced inflammation during escalating bacterial load. The implications of these findings for future therapy of sepsis are discussed. This article is protected by copyright. All rights reserved.