Visualization and characterization of complement activation in acetylcholine receptor antibody seropositive myasthenia gravis

Introduction/Aims There are no blood biomarkers to monitor treatment effects in myasthenia gravis (MG) or studies visualizing the acetylcholine receptor (AChR) antibody‐induced membrane attack complex (MAC) at the human muscle membrane. This study aimed to compare levels of complement activation products and native complement components in MG patients and healthy controls (HCs) and to model the AChR antibody‐mediated attacks in human muscle cells. Methods We assessed the complement components and activation product levels with enzyme‐linked immunosorbent assay and magnetic bead‐based sandwich assays in plasma and sera of 23 MG patients and matched HCs. Receiver operator characteristic (ROC) curve analysis evaluated the diagnostic accuracy. Complement levels were correlated with the myasthenia gravis composite (MGC) scores. AChR+ MG modeling in human muscle cells used sera from nine MG patients and three HCs. Results MG patients had significantly higher plasma levels of C3a (p