Guillain-Barré syndrome: clinical and immunological aspects.

Immune-mediated PNS disorders comprise a significant segment of diseases of the nervous system. Studies on GBS as a prototype of these disorders and its experimental model EAN have helped to elucidate some of the mechanisms responsible for myelin injury in the PNS. These mechanisms, although partially understood have been useful in implementing therapies such as plasmapheresis and IVIG and various other immunomodulators. The question of whether an infectious agent such as a virus can directly damage the myelin sheath and/or Schwann cells or whether the agent triggers an immune response against self through antigenic mimicry remains unanswered. The association between C. jejuni infection and GBS has opened new areas of investigation in understanding the immunopathogenesis of the disease. Similar observations with other environmental factors may be made in the future, pointing to the possibility that GBS may not be caused by a single agent but could be the result of an immunological attack on the PNS myelin assembly by a variety of agents or factors. Regardless of the etiology, if the myelin injury is aggravated by product of the immune cells, such as various cytokines, neutralization of these factors could help lessen the burden of injury to the nerves. Future research in autoimmune disorders of the PNS needs to focus on identifying environmental factors that directly, or indirectly through antigen mimicry, damage the PNS myelin. In parallel, further understanding of the immunopathogenesis by dissecting the immunological phenomenon at the systemic and local levels, especially the role of cytokines, growth factors, and adhesion molecules will pave the way for more rational therapies, even if the causative factors are not known. Studies in laboratory animals have demonstrated the efficacy of selective immunotherapy through modulation of the trimolecular complex, i.e., T cell receptor, MHC/molecule, and antigen. Immunological tolerance, presumably through deletion of autoreactive clones, clonal anergy, or active suppression, has proven effective in animals. Other modes of immunotherapy such as nonspecific depletion of T or B cells or down-regulation of activated cells have also been shown to abolish or decrease the severity of experimental autoimmune neurological disorders, including EAN. These immunotherapeutic modalities may become applicable to human autoimmune neuropathies.