On-Membrane Dynamic Interplay between Anti-GM1 IgG Antibodies and Complement Component C1q

Area of Science:

• Immunology
• Neuroscience
• Microbiology

Background:

• Guillain-Barré syndrome is an autoimmune neuropathy causing acute limb weakness.
• It is often triggered by Campylobacter jejuni infection due to molecular mimicry between bacterial lipo-oligosaccharides and human gangliosides.
• C. jejuni infection leads to IgG1 autoantibodies against GM1, causing complement-mediated motor nerve damage.

Purpose of the Study:

• To elucidate molecular mechanisms linking autoantigen recognition and complement activation in Guillain-Barré syndrome.
• To characterize dynamic interactions of anti-GM1 IgG autoantibodies on ganglioside-incorporated membranes.

Main Methods:

• High-speed atomic force microscopy was used to observe IgG autoantibody interactions on GM1-containing membranes.
• The study investigated the role of staphylococcal protein A in inhibiting IgG ring formation.
• Effects of hinge disulfide modification on IgG ring formation were analyzed.

Main Results:

• Anti-GM1 IgG autoantibodies assembled into hexameric rings on GM1-containing membranes.
• Complement component C1q was specifically recruited to these IgG rings.
• IgG ring formation was dependent on Fc-Fc interactions, enhanced by restricted diffusion, and sensitive to hinge region conformation.

Conclusions:

• IgG assembly into hexameric rings on membranes is a key step in complement activation during Guillain-Barré syndrome.
• These findings provide mechanistic insights into antibody-complement interactions on membranes.
• The study highlights the role of Fc-Fc interactions and molecular conformation in autoimmune nerve injury.