Characterization of a phospholipid antigen reacting with serum antibody in patients with peripheral neuropathies and paraproteinemia

A phospholipid antigen that reacted with the serum antibody from a patient with peripheral neuropathy and paraproteinemia with both impaired sensory and motor functions, but not with sera from patients with only impaired sensory functions and healthy controls, was purified from bovine cauda equina as a minor component with a concentration of about 0.6 μg per gram wet-weight tissue. The structure of the phospholipid was characterized as lysophosphatidylinositol by means of thin-layer chromatography, gas-liquid chromatography, and negative-ion fast-atom-bombardment mass spectrometry. The major fatty acid component of this phospholipid was stearic acid (> 81%). Our data suggest the possible involvement of a lysophospholipid antigen in the immunopathogenesis of peripheral neuropathies with severe motor and sensory dysfunctions. There is an intriguing possibility that the difference in immunoreactivity of serum antibodies may underlie the differential clinical manifestations in patients with peripheral neuropathy and paraproteinemia.