The role of cytokines in Schwann cell damage, protection, and repair.

Cytokines, proteins that are secreted by many cells, including inflammatory and glial cells, mediate interactions between cells, generally through paracrine and autocrine networks. Their effects are highly pleiotropic, with overlap of some activities. The pathogenesis of Guillain-Barré syndrome (GBS), especially the classic inflammatory demyelinating polyneuropathy form, seems to involve lymphocytes and macrophages, which are rich sources of cytokines. Macrophages likely have a role in the pathogenesis of the primarily axonal, less inflammatory forms of GBS. Cytokines appear to be involved in damage to Schwann cells, myelin, and axons, although the exact roles of the different cytokines is uncertain. There is increasing evidence that cytokines, including some proinflammatory cytokines that ordinarily cause damage, may also protect the cells of the peripheral nervous system and aid in its repair. The evolution of inflammatory and demyelinating disorders, including the degree of recovery, is probably dependent on the interactions of the different cytokines.