Effect of Fasciola hepatica excretory-secretory products on the metabolic burst of sheep and human neutrophils

F. hepatica excretory-secretory (ES) products were found to inhibit superoxide output in phorbol myristate acetate (PMA)-stimulated sheep and human neutrophils as measured by spectrophotometry. Luminol-enhanced chemiluminescence by PMA-stimulated neutrophils from both species was again inhibited. However, nitric oxide output by PMA-stimulated human neutrophils was significantly increased in the presence of ES products, whilst in sheep it was inhibited. No major effects were noted using resting neutrophils. The results are discussed in relation to the evolution of parasite defence mechanisms.