Which antibody is commonly targeted in MG?

• A. Acetylcholine receptor antibodies
• B. GABA receptor antibodies
• C. NMDA receptor antibodies
• D. Acetylcholinesterase antibodies

Answer: (A)

In myasthenia gravis, the immune system mostly targets the postsynaptic nicotinic acetylcholine receptors at the neuromuscular junction. When antibodies bind these receptors, they block acetylcholine from activating them and promote receptor loss, so the muscle endplate becomes less responsive. That’s why people experience fatigable weakness and droopy eyelids because repeated use fatigues the weakened transmission.

The most common antibody involved is against the acetylcholine receptor itself. Some patients, especially those who don’t have this antibody, can have antibodies to other components like MuSK or LRP4, which are alternative targets in MG. But the classic and most frequent mechanism is anti-acetylcholine receptor antibodies.

Antibodies to GABA receptors or NMDA receptors are tied to autoimmune encephalitis rather than MG, and antibodies against acetylcholinesterase would affect the enzyme that breaks down acetylcholine rather than the receptor itself—this isn’t the typical basis of MG.