Host-specific evasion of the alternative complement pathway by schistosomes correlates with the presence of a phospholipase C-sensitive surface molecule resembling human decay accelerating factor.
Schistosoma mansoni parasites recovered from the blood stream were found to be nonactivators of the alternative complement pathway (ACP) when exposed to sera of homologous but not heterologous host species. Schistosomes could be converted into activators of the homologous ACP by treatment with phospholipase C. Antibodies to either human or guinea pig decay accelerating factor (DAF), a 70-kDa glycosylphosphatidylinositol anchored membrane glycoprotein which controls ACP activation on the mammalian cell plasma membrane, bound to the surface of immature schistosomes and immunoprecipitated a molecule of similar molecular mass from detergent extracts of surface iodinated parasites. Phospholipase C treatment drastically reduced the reactivity of the worms with the anti-DAF antibodies. These data suggest that schistosomes evade the ACP by inserting functional host DAF into their surfaces, possibly through adsorption of the molecule's lipophilic diacyglycerol membrane anchor moiety into the outer lipid bilayer of the parasite.
Immunology and Cell Biology Section, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
E J
EJ
Pearce
B F
BF
Hall
A
A
Sher
D000327:Adsorption; D000818:Animals; D018958:CD55 Antigens; D002462:Cell Membrane / Q000502:physiology; D003167:Complement Activation; D003169:Complement Inactivator Proteins / Q000502:physiology*; D003170:Complement Pathway, Alternative; D005455:Fluorescent Antibody Technique; D006168:Guinea Pigs; D008253:Macaca mulatta; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D011817:Rabbits; D012550:Schistosoma mansoni / Q000276:immunology*; D010738:Type C Phospholipases / Q000494:pharmacology*
D018958:CD55 Antigens; D003169:Complement Inactivator Proteins; D008565:Membrane Proteins; D010738:Type C Phospholipases