Extracellular myeloperoxidase (MPO) is a macrophage modulator which stimulates release of the pro-inflammatory cytokine TNF alpha in addition to reactive oxygen species (ROS) generated by these cells. MPO-induced macrophage secretion of pro-inflammatory mediators indirectly upregulates neutrophil pro-inflammatory capacity through contributing to neutrophil priming for respiratory burst activity. However, to date the question concerning a direct influence on the neutrophil by MPO or the MPO-derived product hypochlorous acid (HOCl) remains to be elucidated. Taurine, the most abundant free amino acid in human neutrophils acts as an antioxidant through the formation of taurine-chloramine by sequestering HOCl. Zinc also has antioxidant properties and taurine-zinc complexes have been shown to have greater efficacy than either agent alone in protection against ROS-mediated tissue damage. The aims of this study were: (a) to determine if extracellular MPO modulates the inflammatory response through autocrine feedback on the neutrophil and to investigate if taurine either directly or indirectly through taurine-chloramine formation may further influence this pathway and (b) to evaluate the efficacy of a taurine-zinc combination in modulating MPO-induced CD11b receptor expression.Extracellular myeloperoxidase (MPO) is a macrophage modulator which stimulates release of the pro-inflammatory cytokine TNF alpha in addition to reactive oxygen species (ROS) generated by these cells. MPO-induced macrophage secretion of pro-inflammatory mediators indirectly upregulates neutrophil pro-inflammatory capacity through contributing to neutrophil priming for respiratory burst activity. However, to date the question concerning a direct influence on the neutrophil by MPO or the MPO-derived product hypochlorous acid (HOCl) remains to be elucidated. Taurine, the most abundant free amino acid in human neutrophils acts as an antioxidant through the formation of taurine-chloramine by sequestering HOCl. Zinc also has antioxidant properties and taurine-zinc complexes have been shown to have greater efficacy than either agent alone in protection against ROS-mediated tissue damage. The aims of this study were: (a) to determine if extracellular MPO modulates the inflammatory response through autocrine feedback on the neutrophil and to investigate if taurine either directly or indirectly through taurine-chloramine formation may further influence this pathway and (b) to evaluate the efficacy of a taurine-zinc combination in modulating MPO-induced CD11b receptor expression.