the nerve dysfunction in guillain–barré syndrome is caused by an immune attack on the nerve cells of the peripheral nervous system and their support structures. the nerve cells have their body (the soma) in the spinal cord and a long projection (the axon) that carries electrical nerve impulses to the neuromuscular junction where the impulse is transferred to the muscle. axons are wrapped in a sheath of schwann cells that contain myelin. between schwann cells are gaps (nodes of ranvier) where the axon is exposed. different types of guillain–barré syndrome feature different types of immune attack. the demyelinating variant (aidp, see below) features damage to the myelin sheath by white blood cells (t lymphocytes and macrophages); this process is preceded by activation of a group of blood proteins known as complement. in contrast, the axonal variant is mediated by igg antibodies and complement against the cell membrane covering the axon without direct lymphocyte involvement.