<prompt> All of the following statements about Myasthenia Gravis are true, except:Anti-AChR antibodies are the most common antibodies in generalized myasthenia gravisThe pathogenic Anti-AChR antibodies are IgG antibodiesAnti-MuSK antibodies are directed against muscarinic ACh receptorsThe major defect is a decrease in the number of available ACh receptors  <response>: Anti-MuSK antibodies are autoantibodies directed against muscle-specific tyrosine kinase MuSK Anti-ChR antibodies and Anti-MuSK Antibodies directed against muscle-specific tyrosine kinase MuSK Anti-AChR antibodies are the most common antibodies in generalized myasthenia gravis. The pathogenic antibodies aee IgG and are T cell dependent The chief target of the autoimmune attack Anti-AChR antibodies in most cases of myasthenia gravis is the skeletal muscle nicotinic acetylcholine receptor nAChR The underlying defect is a decrease in the number of available Nicotinic ACh Receptors nAChR on the motor end plate at the Neuromuscular junction due to an antibody mediated autoimmune attack. Anti-MuSK antibody occurs in about 40 of patients without AChR antibody. Muscle -specific kinase MuSK is a protein involved in AChR clustering at neuromuscular junctions. An immune response to muscle-specific kinase MuSK, can also result in MG, with reduction of AChR demonstrated experimentally. Anti-MuSK antibody occurs in about 40 of patients without AChR antibody. Ref: Harrison;s 19th edition Pgno: 2701 