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C‐reactive protein binds to immune complexes
Author(s) -
Agrawal Alok,
Radha Hima B,
Cropsey Christopher L,
Suresh Madathilparambil V,
Singh Sanjay K
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.673.9
Subject(s) - immune system , antibody , chemistry , immunoglobulin g , immune complex , receptor , ligand binding assay , antigen antibody complex , antigen , recombinant dna , binding site , microbiology and biotechnology , immunology , biology , biochemistry , gene
C‐reactive protein (CRP) has been shown to bind to Fcγ receptor IIa (also known as CD32). CD32 is present on the cells of the immune system and is the receptor for IgG‐containing immune complexes. In this study, we explored CRP‐CD32 interaction in an ELISA‐based solid‐phase binding assay using recombinant CD32‐coated plates. CRP bound to CD32 in a dose‐dependent manner. Surprisingly, when CD32 was blocked with anti‐CD32 IgG antibody, the binding of CRP to CD32 was not inhibited, suggesting a possible interaction between CRP and CD32‐anti‐CD32 complexes. CRP also bound to immobilized IgG when the plates coated with either normal human IgG or anti‐BSA IgG were used in the assays. The inability of the binding of a mutant form of CRP to immobilized IgG further showed the specificity of CRP‐IgG interaction. CRP also bound to immune complexes prepared from BSA and anti‐BSA antibody, indicating that the presence of the antigen did not affect the binding of CRP to IgG. CRP, however, did not bind to immune complexes in the fluid‐phase. These data suggest that CRP may also bind to immune complex‐occupied CD32‐bearing cells and may modulate intracellular signaling triggered by the binding of immune complexes to CD32. Our findings have implications for the functions of CRP in the antibody‐mediated clearance of pathogens and in immune complex‐mediated pathologic conditions.