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Related Experiment Videos

Engineered antibodies with increased activity to recruit complement.

E E Idusogie1, P Y Wong, L G Presta

  • 1Oncology Department, Aventis-Gencell, Hayward, CA 94545, USA.

Journal of Immunology (Baltimore, Md. : 1950)
|February 13, 2001
PubMed
Summary
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Two key sites in human immunoglobulin G (IgG) were identified to significantly enhance C1q binding and complement-dependent cytotoxicity (CDC). Mutations at K326 and E333 can restore biological activity to inactive IgG isotypes.

Area of Science:

  • Immunology
  • Protein Engineering

Background:

  • Human immunoglobulin G (IgG) effector functions are critical for immune responses.
  • The C(H)2 domain of IgG mediates interactions with complement proteins, such as C1q.
  • Specific residues within the C(H)2 domain are known to influence C1q binding and subsequent complement activation.

Purpose of the Study:

  • To identify and characterize specific residues in human IgG that modulate C1q binding and complement-dependent cytotoxicity (CDC).
  • To investigate the role of residues K326 and E333 in the C(H)2 domain of IgG1 and IgG2.
  • To determine if mutations in these residues can confer or enhance biological activity in previously inactive IgG isotypes.

Main Methods:

  • Site-directed mutagenesis of human IgG1 and IgG2 at specific residues (K326 and E333).

Related Experiment Videos

  • Assays to measure C1q binding affinity.
  • Complement-dependent cytotoxicity (CDC) assays to evaluate biological activity.

    • Main Results:

    • Mutations at K326 and E333 individually or in combination dramatically increased C1q binding and CDC activity in human IgG1.
    • A K326 tryptophan mutation reduced antibody-dependent cell-mediated cytotoxicity (ADCC) activity.
    • Mutations E333 serine and K326 tryptophan in human IgG2 conferred CDC activity to an otherwise inactive wild-type IgG2.

    Conclusions:

    • Residues K326 and E333 are critical determinants of IgG biological activity, particularly C1q binding and CDC.
    • Targeted mutations at these sites can enhance the effector functions of IgG molecules.
    • These findings offer potential strategies for engineering IgG therapeutics with improved efficacy.