Amastigotes of Trypanosoma cruzi escape destruction by the terminal complement components
We studied the effect of complement on two life cycle stages of the protozoan parasite Trypanosoma cruzi: epimastigotes, found in the insect vector, and amastigotes, found in the mammalian host. We found that while both stages activate vigorously the alternative pathway, only epimastigotes are destroyed. The amounts of C3 and C5b-7 deposited on the amastigotes were similar to those bound to the much larger epimastigotes. Binding of C9 to amastigotes was four to six times less than binding to epimastigotes, resulting in a lower C9/C5b-7 ratio. Although a fairly large amount of C9 bound stably to amastigotes, no functional channels were formed as measured by release of incorporated /sup 86/Rb. The bound C9 had the characteristic properties of poly-C9, that is, it expressed a neo-antigen unique to poly-C9, and migrated in SDS-PAGE with an apparent Mr greater than 10(5). The poly-C9 was removed from the surface of amastigotes by treatment with trypsin, indicating that it was not inserted in the lipid bilayer. Modification of amastigote surface by pronase treatment rendered the parasites susceptible to complement attack. These results suggest that amastigotes have a surface protein that binds to the C5b-9 complex and inhibits membrane insertion, thus protecting the parasites from complement-mediated lysis.
- Research Organization:
- New York Univ. Medical Center, NY (USA)
- OSTI ID:
- 5987797
- Journal Information:
- J. Exp. Med.; (United States), Vol. 169:3
- Country of Publication:
- United States
- Language:
- English
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CELL MEMBRANES
LYSIS
COMPLEMENT
BIOCHEMICAL REACTION KINETICS
TRYPANOSOMA
INFECTIVITY
TRYPANOSOMIASIS
PATHOGENESIS
BIOLOGICAL PATHWAYS
ELECTROPHORESIS
INHIBITION
LIFE CYCLE
LIPIDS
RUBIDIUM 86
TRACER TECHNIQUES
TRYPSIN
ALKALI METAL ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
DISEASES
ENZYMES
HYDROLASES
INFECTIOUS DISEASES
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MASTIGOPHORA
MEMBRANES
MINUTES LIVING RADIOISOTOPES
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PARASITES
PARASITIC DISEASES
PEPTIDE HYDROLASES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RUBIDIUM ISOTOPES
SERINE PROTEINASES
550901* - Pathology- Tracer Techniques