Analysis of the recognition mechanism of the alternative pathway of complement by monoclonal anti-factor H antibodies: evidence for multiple interactions between H and surface bound C3b

FEBS Lett. 1996 Sep 16;393(2-3):297-302. doi: 10.1016/0014-5793(96)00905-2.


The ability of the alternative pathway of complement to discriminate targets as either activators or non-activators is mediated by different binding properties of factor H to surface-associated C3b molecules. In the present study we have probed the interaction between H and C3b using five anti-H mAb. The binding sites of the mAb were mapped by Western blotting using both recombinant and trypsin-generated H fragments. Two mAb bound to CCP1 (90X, 196X), two to CCP5 (MRC OX24, 86X) and one to CCP8-15a (131X). At a molar ratio 2:1 of 125I-H:mAb all tested mAb enhanced binding of H to both activator- and non-activator-bound C3b. At higher concentrations two mAb had an inhibitory effect on H binding to surface-associated C3b (OX24, 131X). Thus the mAb 131X inhibits H binding to surface-bound C3b but unlike OX24 it does not bind to the previously described C3b binding site within or near CCP4-5. These results indicate that there is an additional interaction site on factor H for surface-bound C3b.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal
  • Antibody Specificity
  • Binding Sites, Antibody
  • Blotting, Western
  • Complement C3b / analysis
  • Complement C3b / immunology
  • Complement C3b / metabolism*
  • Complement Factor H / analysis
  • Complement Factor H / immunology
  • Complement Factor H / metabolism*
  • Complement Pathway, Alternative*
  • Cross-Linking Reagents
  • Humans
  • Mice
  • Mice, Inbred BALB C
  • Peptide Mapping
  • Radioimmunoassay
  • Recombinant Proteins / analysis
  • Recombinant Proteins / immunology
  • Recombinant Proteins / metabolism
  • Trypsin


  • Antibodies, Monoclonal
  • CFH protein, human
  • Cross-Linking Reagents
  • Recombinant Proteins
  • Complement C3b
  • Complement Factor H
  • Trypsin