We have analyzed the role and regulation of autoantibodies in inflammatory demyelinating polyneuropathy (GBS/CIDP). The clinical significance of pathogenic autoantibodies to peripheral nerve tissue is suggested by the beneficial response of many of these patients to plasmapheresis and treatment with high doses of polyspecific IVIgG. Recovery, whether spontaneous or therapeutically-induced, is associated with anti-idiotypic suppression of the antoantibodies. Preliminary results suggest that these autoantibodies share cross-reactive idiotypes or, alternatively, that the regulatory anti-idiotypic antibodies are multireactive.