How do antibodies cause disease without tissue injury?

Some antibodies may cause disease without directly inducing tissue injury. In some cases of myasthenia gravis, antibodies against the acetylcholine receptor inhibit neuromuscular transmission, causing paralysis. Other antibodies may directly activate receptors, mimicking their physiologic ligands. For example, Graves disease, in which antibodies against the receptor for thyroid-stimulating hormone activate thyroid cells even in the absence of the hormone.