title: Depression of hydrogen peroxide dependent killing of schistosomula in vitro by peritoneal exudate cells from Schistosoma mansoni infected mice.
abstract: Peritoneal exudate cells from mice infected with Schistosoma mansoni (S-PEC) can kill a small proportion of schistosomula in vitro in the presence of immune serum. S-PEC produce a low level of respiratory burst. However, schistosomula mortality in their presence is not reduced when exogenous antioxidants are added, suggesting that with S-PEC, oxidative killing may not be important. Hydrogen peroxide (H2O2) and superoxide production by S-PEC, and cells from Bacillus Calmette-Guerin (BCG) and thioglycollate (THGL) injected mice, nonspecifically stimulated with opsonized zymosan, were measured. Levels of H2O2 produced by S-PEC were significantly lower than BCG or THGL PEC, and were below the threshold for schistosomula killing. This correlated with lower levels of cell-mediated killing of schistosomula in vitro by S-PEC than by BCG-PEC. Superoxide levels, however, were similar between the 3 cell populations. It therefore appears that the efficiency of PEC to kill schistosomules in vitro correlates with H2O2 rather than superoxide levels. It was found that there was a sharp concentration threshold in H2O2 mediated killing of schistosomula. A depression in the levels of H2O2 produced may be a mechanism by which the parasite can partially evade the host immune system.
authors.affiliation: Institute of Parasitology, McGill University, Ste Anne de Bellevue, Quebec, Canada.
authors.forename: J M
authors.initials: JM
authors.lastname: Smith
authors.forename: G M
authors.initials: GM
authors.lastname: Mkoji
authors.forename: R K
authors.initials: RK
authors.lastname: Prichard
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002452:Cell Count; D005122:Exudates and Transudates / Q000166:cytology; D005260:Female; D006861:Hydrogen Peroxide / Q000378:metabolism*; D066298:In Vitro Techniques; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D010529:Peritoneal Cavity / Q000166:cytology; D012550:Schistosoma mansoni / Q000276:immunology*; D012555:Schistosomiasis mansoni / Q000276:immunology*; D013154:Spleen / Q000166:cytology; D013481:Superoxides / Q000378:metabolism; D013864:Thioglycolates / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D013864:Thioglycolates; D013481:Superoxides; D006861:Hydrogen Peroxide