Ing Kao

Myasthenia gravis: passive transfer from man to mouse

Daily injections into mice of an ammonium sulfate-precipitated immunoglobulin fraction of serum from patients with myasthenia gravis were carried out for up to 14 days. The mice showed reduced amplitudes of miniature endplate potentials and reduced numbers of acetylcholine receptors at the neuromuscular junctions. Some mice showed typical decremental responses on repetitive nerve stimulation, with reversal by neostigmine. This represents the first evidence of a circulating factor in the serum of patients with myasthenia gravis which on passive transfer reproduces features of the disease in experimental animals.

Myasthenia gravis. Study of humoral immune mechanisms by passive transfer to mice

To study the role of humoral factors in the pathogenesis of myasthenia gravis, we employed passive transfer of human serum fractions to mice. Immunoglobulins from 16 patients with myasthenia gravis were injected into mice daily for one to 14 days. Typical myasthenic features of reduction in amplitude of miniature end-plate potentials (mean change more than 50 per cent, P less than 0.005) or reduction in acetylcholine receptors at neuromuscular junctions (mean change more than 50 per cent, P less than 0.005) (or both) were produced by immunoglobulin from 15 of the 16 patients. Some mice showed weakness or decremental responses to repetitive nerve stimulation as well. The active fraction was identified as IgG by three different purification methods. Its effect was enhanced by the third component (C3) of the complement system, but the fifth component (C5) had no effect. These data suggest that the pathogenesis of myasthenia gravis often involves and antibody-mediated autoimmune attack on the acetylcholine receptors of the neuromuscular junction.

MYASTHENIA GRAVIS AS A RECEPTOR DISORDER

Although it is generally accepted that the basic abnormality in myasthenia gravis involves the neuromuscular junction, the exact site and nature of the defect have remained controversia1.l There has been considerable debate as to whether the nerve terminal,2 the postsynaptic region of muscle,:{ or both* are affected by the disease process. The important observation of a reduction in the amplitude of miniature end-plate potentials (MEPPs) was originally interpreted as evidence in favor of a presynaptic defect.5 However, there are several theoretically possible explanations for the small MEPPs and other physiological features of myasthenia gravis (FIGURE l ) , including a reduced amount of acetylcholine (ACh) per quantum, a “false” transmitter, or a reduction in the available ACh receptors at neuromuscular junctions. This presentation will review the current status of work in our laboratory which has focused on the receptor abnormality and its possible role in the pathophysiology of myasthenia gravis.

Myasthenia gravis: übertragbarer „myasthenogener“ Faktor im Serum von Patienten

SummaryRecent evidence indicates that patients with myasthenia gravis (MG) have a reduced number of acetylcholine receptors (Ach-R) at the neuromuscular junction. It has been shown that this abnormality by itself, when produced experimentally, may induce all electrophysiological signs of MG. Furthermore, autoantibodies against human Ach-R have been detected in the serum of patients with MG. It has been proposed that serum autoantibodies may produce the symptomatology of the disease. The purpose of this study was to evaluate whether prolonged exposure to a MG serum fraction in vivo might serve to bring about the myasthenic disorder.A 33% ammonium sulfate precipitated fraction of serum from 9 patients with MG was injected daily into BDF1 mice for up to 14 days. The amount of IgG in this fraction equaled 10–15 mg per single injection. The mice showed reduced amplitudes of the miniature endplate potentials in the diaphragm (mean reduction by 65%), and a reduced number of Ach-R available for 125I-α-bungarotoxin binding (mean reduction by 38% in the extensor digitorum m. and 54% in the soleus m.). In some of the mice a decremental response on repetitive nerve stimulation and clinical signs of muscle weakness could also be demonstrated.None of the animals injected with the immunoglobulin fraction from control sera developed these abnormalities. The results indicate that the immunoglobulin fraction of MG serum contains a transferable “myasthenogenic” factor, presumably an antibody, which is able to bring about many of the characteristic features of MG. These findings provide support for the concept of MG as an autoimmune disease.ZusammenfassungAus Serum von 9 Patienten mit Myasthenia gravis (MG) wurde durch Ausfällung mit Ammoniumsulfat eine Immunglobulinfraktion gewonnen. Diese Fraktion wurde BDF1-Mäusen bis zu einer Gesamtdauer von 14 Tagen einmal täglich intraperitoneal injiziert. Bei den Mäusen zeigte sich eine Reduktion der Amplituden der Miniatur-Endplatten-potentiale im Zwerchfell um durchschnittlich 65% gegenüber Kontrolltieren. Die Bestimmung der Zahl der Acetylcholinreceptoren an der motorischen Endplatte ergab eine Erniedrigung um 38% im M. extensor digitorum longus und um 54% im M. soleus. Einige der Mäuse wiesen bei repetitiver Nervenstimulation einen neuromuskulären Block auf. Klinische Zeichen von Muskelschwäche traten nur bei einem Teil der Tiere auf.Diese Ergebnisse weisen auf die Existenz eines übertragbaren „myasthenogenen“ Faktors, vermutlich eines Antikörpers, im Serum von Patienten mit MG hin. Die Vorstellung, daß die MG eine Autoimmunkrankheit darstellt, erfährt durch diese Untersuchungen wesentliche Stützung.

[A transferable "Myasthenogenic" factor in the serum of patients with myasthenia gravis.].

SummaryRecent evidence indicates that patients with myasthenia gravis (MG) have a reduced number of acetylcholine receptors (Ach-R) at the neuromuscular junction. It has been shown that this abnormality by itself, when produced experimentally, may induce all electrophysiological signs of MG. Furthermore, autoantibodies against human Ach-R have been detected in the serum of patients with MG. It has been proposed that serum autoantibodies may produce the symptomatology of the disease. The purpose of this study was to evaluate whether prolonged exposure to a MG serum fraction in vivo might serve to bring about the myasthenic disorder.A 33% ammonium sulfate precipitated fraction of serum from 9 patients with MG was injected daily into BDF1 mice for up to 14 days. The amount of IgG in this fraction equaled 10–15 mg per single injection. The mice showed reduced amplitudes of the miniature endplate potentials in the diaphragm (mean reduction by 65%), and a reduced number of Ach-R available for 125I-α-bungarotoxin binding (mean reduction by 38% in the extensor digitorum m. and 54% in the soleus m.). In some of the mice a decremental response on repetitive nerve stimulation and clinical signs of muscle weakness could also be demonstrated.None of the animals injected with the immunoglobulin fraction from control sera developed these abnormalities. The results indicate that the immunoglobulin fraction of MG serum contains a transferable “myasthenogenic” factor, presumably an antibody, which is able to bring about many of the characteristic features of MG. These findings provide support for the concept of MG as an autoimmune disease.ZusammenfassungAus Serum von 9 Patienten mit Myasthenia gravis (MG) wurde durch Ausfällung mit Ammoniumsulfat eine Immunglobulinfraktion gewonnen. Diese Fraktion wurde BDF1-Mäusen bis zu einer Gesamtdauer von 14 Tagen einmal täglich intraperitoneal injiziert. Bei den Mäusen zeigte sich eine Reduktion der Amplituden der Miniatur-Endplatten-potentiale im Zwerchfell um durchschnittlich 65% gegenüber Kontrolltieren. Die Bestimmung der Zahl der Acetylcholinreceptoren an der motorischen Endplatte ergab eine Erniedrigung um 38% im M. extensor digitorum longus und um 54% im M. soleus. Einige der Mäuse wiesen bei repetitiver Nervenstimulation einen neuromuskulären Block auf. Klinische Zeichen von Muskelschwäche traten nur bei einem Teil der Tiere auf.Diese Ergebnisse weisen auf die Existenz eines übertragbaren „myasthenogenen“ Faktors, vermutlich eines Antikörpers, im Serum von Patienten mit MG hin. Die Vorstellung, daß die MG eine Autoimmunkrankheit darstellt, erfährt durch diese Untersuchungen wesentliche Stützung.

Myasthenia gravis: übertragbarer „myasthenogener“ Faktor im Serum von Patienten@@@A transferable “Myasthenogenic” factor in the serum of patients with myasthenia gravis: Elektrophysiologische und radiochemische Untersuchungen

SummaryRecent evidence indicates that patients with myasthenia gravis (MG) have a reduced number of acetylcholine receptors (Ach-R) at the neuromuscular junction. It has been shown that this abnormality by itself, when produced experimentally, may induce all electrophysiological signs of MG. Furthermore, autoantibodies against human Ach-R have been detected in the serum of patients with MG. It has been proposed that serum autoantibodies may produce the symptomatology of the disease. The purpose of this study was to evaluate whether prolonged exposure to a MG serum fraction in vivo might serve to bring about the myasthenic disorder.A 33% ammonium sulfate precipitated fraction of serum from 9 patients with MG was injected daily into BDF1 mice for up to 14 days. The amount of IgG in this fraction equaled 10–15 mg per single injection. The mice showed reduced amplitudes of the miniature endplate potentials in the diaphragm (mean reduction by 65%), and a reduced number of Ach-R available for 125I-α-bungarotoxin binding (mean reduction by 38% in the extensor digitorum m. and 54% in the soleus m.). In some of the mice a decremental response on repetitive nerve stimulation and clinical signs of muscle weakness could also be demonstrated.None of the animals injected with the immunoglobulin fraction from control sera developed these abnormalities. The results indicate that the immunoglobulin fraction of MG serum contains a transferable “myasthenogenic” factor, presumably an antibody, which is able to bring about many of the characteristic features of MG. These findings provide support for the concept of MG as an autoimmune disease.ZusammenfassungAus Serum von 9 Patienten mit Myasthenia gravis (MG) wurde durch Ausfällung mit Ammoniumsulfat eine Immunglobulinfraktion gewonnen. Diese Fraktion wurde BDF1-Mäusen bis zu einer Gesamtdauer von 14 Tagen einmal täglich intraperitoneal injiziert. Bei den Mäusen zeigte sich eine Reduktion der Amplituden der Miniatur-Endplatten-potentiale im Zwerchfell um durchschnittlich 65% gegenüber Kontrolltieren. Die Bestimmung der Zahl der Acetylcholinreceptoren an der motorischen Endplatte ergab eine Erniedrigung um 38% im M. extensor digitorum longus und um 54% im M. soleus. Einige der Mäuse wiesen bei repetitiver Nervenstimulation einen neuromuskulären Block auf. Klinische Zeichen von Muskelschwäche traten nur bei einem Teil der Tiere auf.Diese Ergebnisse weisen auf die Existenz eines übertragbaren „myasthenogenen“ Faktors, vermutlich eines Antikörpers, im Serum von Patienten mit MG hin. Die Vorstellung, daß die MG eine Autoimmunkrankheit darstellt, erfährt durch diese Untersuchungen wesentliche Stützung.