The anti- acetylcholine receptor (AChR) antibodies in myasthenia gravis reduce the number of available AChRs at neuromuscular junctions with which of the following mechanism ?: (A) accelerated turnover of AChRs, (B) damage to the postsynaptic muscle membrane, (C) blockade of the active site of the AChR, (D) all of the above
Answer is D. The anti-AChR antibodies reduce the number of available AChRs at NMJs by three distinct mechanisms: (1) accelerated turnover of AChRs by a mechanism involving cross-linking and rapid endocytosis of the receptors; (2) damage to the postsynaptic muscle membrane by the antibody in collaboration with complement; and (3) blockade of the active site of the AChR. Ref harrison 20th edition page 3232