Phagocytosis of live and dead Escherichia coli and Staphylococcus aureus in human whole blood is markedly reduced by combined inhibition of C5aR1 and CD14

Abstract

<i>Background</i> - Sepsis is a dysregulated host response to infection. The aim of this study was to investigate the effects of complement- and CD14 inhibition on phagocytosis of live and dead Gram-negative and Gram-positive bacteria in human whole blood.<p>

<p><i>Methods</i> - Lepirudin-anticoagulated blood was incubated with live or dead <i>E. coli</i> or <i>S. aureus</i> at 37 °C for 120 min with or without the C5aR1 antagonist PMX53 and/or anti-CD14. Granulocyte and monocyte phagocytosis were measured by flow cytometry, and five plasma cytokines by multiplex, yielding a total of 28 mediators of inflammation tested for.<p>

<p><i>Results</i> - 16/28 conditions were reduced by PMX53, 7/28 by anti-CD14, and 24/28 by combined PMX53 and CD14 inhibition. The effect of complement inhibition was quantitatively more pronounced, in particular for the responses to <i>S. aureus</i>. The effect of anti-CD14 was modest, except for a marked reduction in INF-β. The responses to live and dead <i>S. aureus</i> were equally inhibited, whereas the responses to live <i>E. coli</i> were inhibited less than those to dead <i>E. coli</i>.<p>

<p><i>Conclusion</i> - C5aR1 inhibited phagocytosis-induced inflammation by live and dead <i>E. coli</i> and <i>S. aureus</i>. CD14 blockade potentiated the effect of C5aR1 blockade, thus attenuating inflammation.