A client with Guillain-Barré syndrome reports increasing weakness in the legs. Which statement by the nurse describes this symptom?

"The leg weakness is caused by reduced blood flow to the peripheral nerves."

"The leg weakness is caused by psychological stress, temporarily affecting nerve function."

"The leg weakness is caused by immune damage to the myelin sheath of the nerves."

"The leg weakness is caused by prolonged immobility and muscle disuse."