SERUM IGG ANTIBODIES TO A 35-KDA P0-RELATED GLYCOPROTEIN IN MOTOR-NEURON DISEASE

Using an immunoblot technique we found a significantly higher frequenc e of serum IgG antibodies to a 35-kDa peripheral nerve myelin glycopro tein in patients with motor neuron disease (MND) (39% of 70) than in p atients with neuropathy (13% of 61), other neurological diseases (9% o f 32) and normal subjects (5% of 20) (P < 0.005 in all cases), but not with multiple sclerosis (MS) (20% of 30) or non-neural immune disease s (25% of 32). Most positive patients had antibody titers of 1:200 or 1:2000 while higher titers were only found in seven patients with MND, one with chronic inflammatory demyelinating neuropathy, two with MS, two with non-neural immune diseases and one with stroke. The reacting protein had a higher molecular mass than P0 and was only faintly bound by an anti-P0 antiserum, but had the same N-terminal amino acid seque nce of P0. The difference in molecular mass between P0 and the 35-kDa protein and the IgG reactivity of one patient's IgG with the 35-kDa pr otein persisted after its deglycosylation and dephosphorylation. Altho ugh there is no evidence that these antibodies are pathogenic, their f requent occurrence in MND and other immune-mediated conditions support s the hypothesis of an activation of the immune system in MND.