Final answer:
Myasthenia gravis is caused by autoantibodies targeting the acetylcholine receptors at the neuromuscular junction, leading to muscle weakness that improves with rest. The correct answer to the question is B. Acetylcholine receptor.
Step-by-step explanation:
Myasthenia Gravis and its Targets
Myasthenia gravis is an autoimmune disease characterized by the production of autoantibodies that specifically target the acetylcholine receptors (AChR) at the neuromuscular junction. This leads to muscle weakness which notably improves with rest. The autoantibodies involved are high-affinity Immunoglobulin G (IgG) that impair neuromuscular transmission through several mechanisms. They block the receptors for acetylcholine on muscle cells, preventing normal muscle contraction and leading to various symptoms including muscle weakness and fatigue. Treatment may include medications to suppress the immune system or counter the effects of these autoantibodies on the acetylcholine receptors.
In the context of the question provided, the answer would be B. Autoantibodies against the acetylcholine receptor lead to the muscle weakness seen in myasthenia gravis.