title: Ultrastructural characterization of serum-induced changes in the tegument of Taenia taeniaeformis.
abstract: The objective of this study was to characterize complement-dependent damage to the tegument of isolated metacestodes of Taenia taeniaeformis caused by exposure to immune or normal rat serum (IRS and NRS, respectively). Metacestodes of T. taeniaeformis (34- and 69-day-old) from rats were incubated for 1 hr in 0.85% physiological saline solution (PSS), IRS, NRS, heat-inactivated at 56 C for 1 hr (delta) IRS, or delta NRS and then fixed for 2 hr in 3% glutaraldehyde. The larvae were then prepared for freeze-etching, thin sectioning, and SEM by standard techniques. Freeze-etch replicas of PSS-, delta IRS-, and delta NRS-treated larvae showed no damage, whereas those of IRS- and NRS-treated metacestodes exhibited vesiculation in the extracellular matrices, segmentation or "beading" of the microthrix tip, significant reductions in the number of intramembranous particles (IMP) in the P face of the membrane of the microthrix base, and changes in the pattern of IMP distribution in the P face of the base. Similar results were obtained from larvae prepared for thin sectioning and SEM. Additionally, thin-sectioned preparations demonstrated that in some cases the entire tegument was stripped away in IRS- and NRS-treated metacestodes. Our results have provided supportive evidence that complement-mediated lysis of larvae of T. taeniaeformis is not enhanced by the presence of antibody in serum, and we also characterized ultrastructurally the types of tegumental damage that may contribute to lysis. In addition, a possible defense mechanism used by the parasite to counter immunological attack by host phagocytic cells is proposed.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure; D003165:Complement System Proteins / Q000276:immunology*; D005613:Freeze Etching; D007106:Immune Sera / Q000276:immunology; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D051381:Rats; D013621:Taenia / Q000276:immunology* / Q000648:ultrastructure
chemical_list: D007106:Immune Sera; D003165:Complement System Proteins