Factors defining target specificity in antibody-mediated neuropathy: Density-dependent binding of anti-GD(1a) polyclonal IgG from a neurological patient

IgM and IgG antibodies reacting with components of human brain gangliosides were detected in a patient bearing severe sensory ataxy. Using different chemical and immunological methods, the antigen was identified as the GD(1a) ganglioside. The antibodies showed antigen 'density-dependent' binding, a property only observed in tumor-specific monoclonal antibodies. The relevance of this result in regard with target specificity of neuropathy- associated antibodies directed to ubiquitous glycolipids is discussed.