Autoimmune attack on muscle receptors in myasthenia gravis Steps:

• Identify myasthenia gravis as an autoimmune disorder affecting neuromuscular junctions.
• Recall that symptoms arise from impaired muscle contraction due to blocked acetylcholine signaling.
• Examine choices for accurate description of antibody role at muscle cell membranes.
• Select the option matching antibody blockade of receptors, causing weakness and fatigue.

Why B is correct:

• In myasthenia gravis, autoantibodies bind to and block acetylcholine receptors on muscle cell membranes, preventing neurotransmitter action and leading to symptoms like muscle fatigue.

Why the others are wrong:

• A: Self-antigens do not attack antibodies; instead, autoantibodies target self-antigens on muscle cells.
• C: T-lymphocytes are not destroyed; the issue involves autoantibodies, not T-cell loss.
• D: Receptors lost are on muscle cells at neuromuscular junctions, not nerve cells in the spinal cord.

Final answer: B