suffering from ulcerative colitis and Guillain-Barré syndrome, a rare and nasty disorder. Here, our elegant defense, the immune system, turns against the lining that coats the ends of long nerve cells that extend along the periphery of the body. The linings of the nerves, known as myelin sheaths, are crucial because they help the body to quickly and efficiently transmit information by insulating these cells and, in effect, keeping out other information. In Merredith’s mother, though, T cells and B cells had begun to cooperate in attacking the myelin sheaths. “Guillain-Barré is called a
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