Clinical application of clustered-AChR for the detection of SNMG

Area of Science:

• Neuroimmunology
• Autoimmune Diseases
• Neuromuscular Junction Disorders

Background:

• Myasthenia gravis (MG) is an autoimmune disorder affecting the neuromuscular junction (NMJ).
• A subset of MG patients, termed serum-negative MG (SNMG), lack detectable anti-acetylcholine receptor (AChR) antibodies via standard assays.
• SNMG patients exhibit clinical symptoms similar to antibody-positive MG, suggesting the presence of undetected antibodies.

Purpose of the Study:

• To investigate the hypothesis that SNMG patients possess low-affinity anti-AChR antibodies.
• To develop a sensitive method for detecting these antibodies by targeting AChRs clustered at high density, mimicking the NMJ.
• To improve the diagnostic rate for serum-negative myasthenia gravis.

Main Methods:

• Expressed AChR subunits with the clustering protein rapsyn in human embryonic kidney (HEK) cells.
• Utilized immunofluorescence and fluorescence-activated cell sorting (FACS) to detect antibody binding to clustered AChRs.
• Applied this cell-based assay to sera from SNMG patients.

Main Results:

• Anti-AChR antibodies binding to rapsyn-clustered AChRs were detected in 45.83% (11/24) of SNMG patients.
• This represents the first application of cell-based AChR antibody detection in China.
• The developed method demonstrated significant sensitivity and specificity.

Conclusions:

• A novel cell-based assay can detect low-affinity anti-AChR antibodies in a substantial proportion of SNMG patients.
• This approach enhances the diagnostic yield for serum-negative myasthenia gravis.
• The findings underscore the utility of targeting clustered receptors for improved autoimmune diagnostics.