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Properdin can initiate complement activation by binding specific target surfaces and providing a platform for de novo convertase assembly.
- Source :
-
Journal of immunology (Baltimore, Md. : 1950) [J Immunol] 2007 Aug 15; Vol. 179 (4), pp. 2600-8. - Publication Year :
- 2007
-
Abstract
- Complement promotes the rapid recognition and elimination of pathogens, infected cells, and immune complexes. The biochemical basis for its target specificity is incompletely understood. In this report, we demonstrate that properdin can directly bind to microbial targets and provide a platform for the in situ assembly and function of the alternative pathway C3 convertases. This mechanism differs from the standard model wherein nascent C3b generated in the fluid phase attaches nonspecifically to its targets. Properdin-directed complement activation occurred on yeast cell walls (zymosan) and Neisseria gonorrhoeae. Properdin did not bind wild-type Escherichia coli, but it readily bound E. coli LPS mutants, and the properdin-binding capacity of each strain correlated with its respective serum-dependent AP activation rate. Moreover, properdin:single-chain Ab constructs were used to direct serum-dependent complement activation to novel targets. We conclude properdin participates in two distinct complement activation pathways: one that occurs by the standard model and one that proceeds by the properdin-directed model. The properdin-directed model is consistent with a proposal made by Pillemer and his colleagues >50 years ago.
- Subjects :
- Animals
Antibodies chemistry
Antibodies genetics
Antibodies metabolism
Complement C3 Convertase, Alternative Pathway metabolism
Escherichia coli Infections genetics
Escherichia coli Infections metabolism
Escherichia coli K12 genetics
Escherichia coli K12 metabolism
Gonorrhea metabolism
Humans
Lipopolysaccharides metabolism
Mutation
Neisseria gonorrhoeae metabolism
Properdin genetics
Properdin metabolism
Protein Binding
Rabbits
Recombinant Fusion Proteins chemistry
Recombinant Fusion Proteins genetics
Recombinant Fusion Proteins metabolism
Sheep
U937 Cells
Zymosan metabolism
Complement C3 Convertase, Alternative Pathway chemistry
Complement Pathway, Alternative
Escherichia coli K12 chemistry
Lipopolysaccharides chemistry
Neisseria gonorrhoeae chemistry
Properdin chemistry
Zymosan chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 0022-1767
- Volume :
- 179
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Journal of immunology (Baltimore, Md. : 1950)
- Publication Type :
- Academic Journal
- Accession number :
- 17675523
- Full Text :
- https://doi.org/10.4049/jimmunol.179.4.2600