Figure 8.

The role of Hx in neutrophil chemotaxis. The pathogenesis of severe infectious diseases is associated with hemolysis and secondary release of cell-free heme. LPS and heme synergize to induce the production of TNF, IL-6 and LTB4 from monocytes/macrophages. LTB4 induces neutrophil migration. Two hypotheses might explain the effect of Hx to suppress chemotaxis of neutrophils: hypothesis I, Hx binds heme and therefore blocks synergistic production of LTB4 and other chemotaxins, secondarily decreasing the signal for the chemotaxis of neutrophils; hypothesis II, Hx itself has protease activity and direct inhibitory effect on the neutrophil migration. The results from this paper support hypothesis I.