Document Detail

Identification of C3 acceptors responsible for complement activation in Crithidia fasciculata.
MedLine Citation:
PMID:  3143825     Owner:  NLM     Status:  MEDLINE    
Crithidia fasciculata, an insect trypanosomatid is readily lysed by normal human serum at concentrations as low as 3%. Lysis occurs in the presence of Mg+2-EGTA and is antibody independent, indicating that the alternative pathway of complement activation is involved. Analysis of [131I]C3 deposition on C. fasciculata cells using C8-deficient serum, revealed that about 4 x 10(5) C3 molecules bound to each cell. Most of the C3 was bound to cells as C3b, part of it forming high molecular weight complexes, which could be dissociated by methylamine treatment at alkaline pH. To characterize the C3 acceptors on C. fasciculata, surface-iodinated cells were incubated with C8D or heat-inactivated serum, extracted and immunoprecipitated with anti-C3 or anti-arabinogalactan antisera. Analysis of the immunoprecipitated material on SDS gels showed high-molecular weight components, which disappeared after methylamine treatment, giving rise to a component of 200 kDa molecular size. This 200-kDa component corresponded to a purified arabinogalactan complex, which was immunoprecipitated from labeled cell extracts, without incubation with C8D, using anti-arabinogalactan antibodies. These results suggest that the arabinogalactan glycoconjugate is a C3 acceptor in C. fasciculata during complement activation. Purified arabinogalactan complexes were able to inactivate C3 in vitro. Solubilization in KOH to cleave the peptide moiety rendered it unable to inactivate C3. Apparently, the aggregated state of the purified arabinogalactan component at the cell surface is important for C3 deposition and activation.
M L Güther; L R Travassos; S Schenkman
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of protozoology     Volume:  35     ISSN:  0022-3921     ISO Abbreviation:  J. Protozool.     Publication Date:  1988 Nov 
Date Detail:
Created Date:  1989-01-13     Completed Date:  1989-01-13     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985197R     Medline TA:  J Protozool     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  475-80     Citation Subset:  IM    
Escola Paulista de Medicina, São Paulo, Brazil.
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MeSH Terms
Complement Activation*
Complement C3 / immunology
Complement Pathway, Alternative*
Crithidia / immunology*
Egtazic Acid / diagnostic use
Electrophoresis, Polyacrylamide Gel
Galactans / immunology*,  isolation & purification
Iodine Radioisotopes / diagnostic use
Macrophage-1 Antigen
Receptors, Complement / isolation & purification,  physiology*
Reg. No./Substance:
0/Complement C3; 0/Galactans; 0/Iodine Radioisotopes; 0/Macrophage-1 Antigen; 0/Receptors, Complement; 67-42-5/Egtazic Acid

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