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Updated: Jan 19, 2026
Identification of Mouse and Human Antibody Repertoires by Next-Generation Sequencing
Published on: March 15, 2019
Functional, Biophysical, and Structural Characterization of Human IgG1 and IgG4 Fc Variants with Ablated Immune
Susan H Tam1, Stephen G McCarthy2, Anthony A Armstrong3
1Janssen Research & Development, LLC, 1400 McKean Road, Spring House, Ambler, PA 19477, USA. susanhtam@gmail.com.
Engineered IgG1 and IgG4 antibodies, termed IgG1σ and IgG4σ, exhibit minimal immune effector functions. These variants maintain therapeutic properties while reducing unwanted immune responses, showing promise for novel antibody therapies.
Area of Science:
- Immunology
- Biotechnology
- Structural Biology
Background:
- Therapeutic antibodies engineered with modified Fc domains can block immune cell interactions.
- Previous work established an IgG2 variant (IgG2σ) with reduced Fc effector functions.
- IgG1 and IgG4 subtypes offer potential advantages over IgG2 for therapeutic applications.
Purpose of the Study:
- To engineer and evaluate IgG1 and IgG4 variants (IgG1σ, IgG4σ) with eliminated immune effector functions.
- To assess the in vitro and in vivo performance of these novel Fc variants.
- To investigate the structural basis for the reduced Fc-mediated activity.
Main Methods:
- Generation of IgG1σ and IgG4σ variants.
- In vitro assays: antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), antibody-dependent cellular phagocytosis (ADCP), Fcγ receptor binding.
- In vivo assays: T-cell activation in mice, pharmacokinetic studies in human FcRn-transgenic mice and cynomolgus monkeys.
- In silico T-cell epitope analysis.
- X-ray crystallography and molecular simulations of Fc domains.
Main Results:
- IgG1σ and IgG4σ variants demonstrated significantly reduced or undetectable Fc effector functions across multiple assays.
- These variants exhibited comparable or lower Fc-related activities than the IgG2σ control.
- Pharmacokinetic profiles were typical for human IgG1, with good solubility and stability.
- In silico analyses predicted low immunogenicity in humans.
- Structural studies elucidated the mechanisms behind the lack of Fc-mediated immune activity.
Conclusions:
- Engineered IgG1σ and IgG4σ variants effectively eliminate immune effector functions while retaining desirable Fc characteristics.
- These variants represent promising candidates for therapeutic antibodies and Fc fusions requiring an immunologically "silent" Fc domain.
- The findings support the development of safer and more effective antibody-based therapies.
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