Immunoglobulin G/adverse effects; Immunoglobulin G/blood; Myasthenia Gravis/blood; Neuromuscular Junction Diseases/complications; Receptor Protein-Tyrosine Kinases/immunology; Receptors, Cholinergic/immunology; Action Potentials/drug effects; Adult; Animals; Autoantibodies/blood; Disease Models, Animal; Electromyography; Female; Humans; Male; Mice; Mice, Inbred C57BL; Mice, SCID; Microscopy, Electron, Transmission; Middle Aged; Motor Endplate/drug effects; Motor Endplate/physiopathology; Muscle Contraction/drug effects; Muscle Strength/drug effects; Muscle Strength/physiology; Myasthenia Gravis/complications; Myasthenia Gravis/immunology; Myasthenia Gravis/therapy; Neural Conduction/drug effects; Neural Conduction/physiology; Neuromuscular Junction/drug effects; Neuromuscular Junction/pathology; Neuromuscular Junction/physiopathology; Neuromuscular Junction/ultrastructure; Neuromuscular Junction Diseases/pathology; Plasmapheresis/methods; Young Adult