The effects of myasthenic immunoglobulin G on the ultrastructure of mouse motor endplate

Abstract

The effects of immunoglobulin G (IgG), taken from a patient with myasthenia gravis (MG), were studied on the ultrastructure of mouse diaphragm. IgG from a normal patient served as control. After chronic intraperitoneal injection of IgG isolated from the normal patient, the axon terminal of the mouse diaphragm was filled with numerous synaptic vesicles, mitochondria as well as occasional bundles of fine neurofilaments and neurotubules. Primary and secondary synaptic clefts appeared normal. Similar results showed in the axon terminal of the mouse chronically injected with IgG from MG patient. No significant ultrastructure changes were found in the motor endplate of mouse injected chronically with IgG from a MG patient compared with the motor endplate of mouse injected chronically with IgG from normal patient. It is postulated that IgG from MG may not exert morphological changes on the mouse diaphragm, even after chronic intraperitoneal injection.