5W5M

Crystal structure of human IgG4-Sigma1 Fc fragment

Summary for 5W5M

• Entry DOI: 10.2210/pdb5w5m/pdb
• Descriptor: Immunoglobulin heavy constant gamma 4, beta-D-galactopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-2)-alpha-D-mannopyranose-(1-6)-[2-acetamido-2-deoxy-beta-D-glucopyranose-(1-2)-alpha-D-mannopyranose-(1-3)]beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-[alpha-L-fucopyranose-(1-6)]2-acetamido-2-deoxy-beta-D-glucopyranose, GLYCEROL, ... (5 entities in total)
• Functional Keywords: fc, immunoglobulin fold, immune system
• Biological source: Homo sapiens (Human)
• Total number of polymer chains: 2
• Total formula weight: 53554.55

Authors

Armstrong, A.A.,Gilliland, G.L. (deposition date: 2017-06-15, release date: 2017-09-13, Last modification date: 2020-07-29)

Primary citation

Tam, S.H.,McCarthy, S.G.,Armstrong, A.A.,Somani, S.,Wu, S.J.,Liu, X.,Gervais, A.,Ernst, R.,Saro, D.,Decker, R.,Luo, J.,Gilliland, G.L.,Chiu, M.L.,Scallon, B.J.
Functional, Biophysical, and Structural Characterization of Human IgG1 and IgG4 Fc Variants with Ablated Immune Functionality.
Antibodies, 6:-, 2017

PubMed Abstract: Engineering of fragment crystallizable (Fc) domains of therapeutic immunoglobulin (IgG) antibodies to eliminate their immune effector functions while retaining other Fc characteristics has numerous applications, including blocking antigens on Fc gamma (Fcγ) receptor-expressing immune cells. We previously reported on a human IgG2 variant termed IgG2σ with barely detectable activity in antibody-dependent cellular cytotoxicity, phagocytosis, complement activity, and Fcγ receptor binding assays. Here, we extend that work to IgG1 and IgG4 antibodies, alternative subtypes which may offer advantages over IgG2 antibodies. In several in vitro and in vivo assays, the IgG1σ and IgG4σ variants showed equal or even lower Fc-related activities than the corresponding IgG2σ variant. In particular, IgG1σ and IgG4σ variants demonstrate complete lack of effector function as measured by antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, antibody-dependent cellular phagocytosis, and in vivo T-cell activation. The IgG1σ and IgG4σ variants showed acceptable solubility and stability, and typical human IgG1 pharmacokinetic profiles in human FcRn-transgenic mice and cynomolgus monkeys. In silico T-cell epitope analyses predict a lack of immunogenicity in humans. Finally, crystal structures and simulations of the IgG1σ and IgG4σ Fc domains can explain the lack of Fc-mediated immune functions. These variants show promise for use in those therapeutic antibodies and Fc fusions for which the Fc domain should be immunologically "silent".

PubMed: 31548527
DOI: 10.3390/antib6030012

Experimental method

X-RAY DIFFRACTION (1.9 Å)