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Binding of model soluble immune complexes to modified C-reactive protein
M Motie1, S Brockmeier, L A Potempa
1Immtech International, Inc., Evanston, IL 60201, USA.
Journal of Immunology (Baltimore, Md. : 1950)
|June 1, 1996
Summary
Modified C-reactive protein (mCRP) selectively binds immune complexes at acidic pH, with high affinity for aggregated IgG. This interaction, localized to specific mCRP sequences, suggests a role in clearing immune complexes during inflammation.
Area of Science:
- Immunology
- Biochemistry
Background:
- Modified C-reactive protein (mCRP) is implicated in inflammatory processes.
- Immune complexes play a crucial role in immune responses and disease pathogenesis.
Purpose of the Study:
- To characterize the binding interaction between modified C-reactive protein (mCRP) and model immune complexes.
- To determine the affinity, specificity, pH dependence, and binding site of mCRP for immune complexes.
Main Methods:
- Binding isotherms and competitive binding assays were used to quantify the affinity of mCRP for heat-aggregated IgG (HAG) and monomeric IgG.
- Immune complex binding to mCRP was assessed at varying pH levels.
- mCRP-specific monoclonal antibodies (mAbs) were employed to map the binding sites for immune complexes on mCRP.
Main Results:
- mCRP demonstrated high-affinity binding to HAG (Kd = 1.6 nM) and significantly lower affinity for monomeric IgG (>2000-fold less).
- Immune complex binding to mCRP was optimal at acidic pH 5.5.
- Binding sites for HAG and model immune complexes were mapped to specific sequences on mCRP (residues 130-138 and 200-206).
Conclusions:
- mCRP selectively binds immune complexes with high affinity, particularly in acidic environments characteristic of inflammation.
- These findings suggest that mCRP plays a role in the in vivo clearance of immune complexes and potentiates immune effector functions.