This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
[{'content': 'Myasthenia gravis is an autoimmune disorder and antibodies against which of the following can cause the disease? \nSelect and explain. \nA. Acetylcholine receptors (AchR), B. Muscle specific kinase protein( MUSK), C. Lowdensity lipoprotein receptor related protein 4 (LRP4), D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: MG is an autoimmune disorder most commonly caused by anti- AChR antibodies. The anti-AChR antibodies reduce the number of available AChRs. An immune response to muscle-specific kinase (MuSK), a protein involved in AChR clustering at the NMJ, can also result in MG, with reduction of AChRs demonstrated experimentally. Anti-MuSK antibody occurs in about 10% of patients (about 40% of AChR antibody negative patients), while 1-3% have antibodies to another protein at the NMJ--low-density lipoprotein receptor-related protein 4 (LRP4)--that is also impoant for clustering of AChRs. The pathogenic antibodies are IgG and are T cell dependent. Ref harrison 20th edition page 3232', 'role': 'assistant'}]