Occurrence and isotype of antibodies against peripheral nerve myelin in serum from patients with peripheral neuropathy and healthy controls.

Antibodies against peripheral nerve myelin have previously been demonstrated in serum from patients with peripheral neuropathy and IgM paraproteinaemia, and a causal relationship has been suggested. Using enzyme-linked immunosorbent assay (ELISA), anti-myelin antibodies were found in sera from eight of 16 patients with polyneuropathy and paraproteinaemia, but also in 17% of 109 patients with peripheral neuropathy lacking monoclonal immunoglobulin, including five of 10 patients with Charcot-Marie-Tooth disease, and in 16% of 142 blood donors. The antibodies were mostly of IgM class in the two neuropathy groups, while blood donors had mostly IgA antibodies, and a few subjects of each group had antimyelin antibodies of two different isotypes. Western blot confirmed the ELISA results in a majority of antibody positive sera and revealed a 25-30 kD myelin target antigen for sera from the three groups, and for some of the non-paraproteinaemic sera also a 100 kD myelin target antigen. Our results demonstrate that the presence of serum autoantibodies against peripheral nerve myelin does not necessarily indicate a pathological event.