Effect of Fasciola gigantica somatic extracts and excretory/secretory products on superoxide production by activated neutrophils.

Somatic extracts and excretory/secretory (ES) products from Fasciola gigantica suppress the release of toxic oxygen intermediates by activated sheep neutrophils. At the concentrations used both the somatic extracts and ES products had no effect on neutrophil viability and in both cases the inhibitory effect was reversible. In the somatic extracts, heating or treatment with trypsin destroyed the inhibitory effect. However, the ES products contained at least two immunomodulatory factors. One was less than 10 kDa, the other greater than 50 kDa and both factors were heat and trypsin stable. By acting locally and only causing temporary inhibition of neutrophil function F. gigantica can protect itself from immune mediated oxidative damage without compromising the host's response elsewhere.