Assembly and regulation of the complement amplification loop in blood: therole of C3b-C3b-IgG complexes

Citation
E. Jelezarova et Hu. Lutz, Assembly and regulation of the complement amplification loop in blood: therole of C3b-C3b-IgG complexes, MOL IMMUNOL, 36(13-14), 1999, pp. 837-842
Citations number
42
Categorie Soggetti
Immunology
Journal title
MOLECULAR IMMUNOLOGY
ISSN journal
01615890 → ACNP
Volume
36
Issue
13-14
Year of publication
1999
Pages
837 - 842
Database
ISI
SICI code
0161-5890(199909/10)36:13-14<837:AAROTC>2.0.ZU;2-Q
Abstract
Amplification of complement activation in blood and serum starts on multi-p rotein complexes that act as precursors of an alternative C3 convertase. Am ong these covalently linked C4b-: C3b-, and IgG-containing complexes C3b-C3 b-IgG complexes represent the major species containing C3b and IgG. Recent work on their purification and characterization is discussed. Special empha sis is placed on the arrangement of ester bonds in these complexes and thei r dual type of partial protection from inactivation. Partial protection fro m inactivation is mediated by properdin which binds to these complexes in t he complete absence of any other complement protein. High dose IgG, known t o stimulate inactivation of these complexes, appears to lower properdin bin ding in a process that also involves factor H. Properdin stimulates factor B binding to these complexes and renders them far better precursors of a C3 convertase than C3b. The available information allows a suggestion for a n ew scheme on how the amplification loop is assembled and regulated in blood and serum. (C) 1999 Elsevier Science Ltd. All rights reserved.