Ultrastructural damage of Trypanosoma cruzi epimastigotes exposed to decomplemented immune sera

The susceptibility of Trypanosoma cruzi epimastigotes to lysis by normal or immune sera in a complement-dependent reaction has been reported, but the effects induced directly by immune serum depleted of complement remain unst udied. The aim of this work was to study the ultrastructural alterations in duced in T. cruzi epimastigotes by immune mouse or rabbit sera with or with out complement. A local isolate of T. cruzi (Queretaro) was used in all exp eriments. Immune sera were raised in both mouse and rabbit by immunization with T. cruzi epimastigote antigens. Light microscopy showed intense agglut ination of epimastigotes when incubated with decomplemented mouse or rabbit immune sera. A distinctive ultrastructural feature of this agglutination p attern was the fusion of plasma membranes and a pattern of intercrossing be tween subpellicular microtubules. Agglutination was associated with fragmen tation of nuclear membranes and swelling of cytoplasm, Golgi cisternae, end oplasmic reticulum, mitochondria and kinetoplast membranes. Agglutinated pa rasites also incorporated trypan blue stain. Results of [H-3]-thymidine inc orporation confirmed that epimastigotes exposed to specific antibodies in t he absence of complement were incapable of proliferating. Ultrastructural c hanges observed in epimastigote micrographs incubated with decomplemented i mmune mouse sera were statistically significant (P <0.001) when compared wi th results obtained from images after incubation with decomplemented normal mouse sera.