Antibodies from down's syndrome patients bind to the same cholinergic neurofilament protein recognized by alzheimer's disease antibodies

Down's syndrome (DS) patients who survive beyond the third decade develop brain lesions characteristic of Alzheimer's disease (AD). Sera of AD patients contain antibodies that bind specifically to the heavy neurofilament protein (NF–H) of Torpedo cholinergic neurons. In the present report, we examined whether the AD–like pathologic changes in DS are associated with the existence of such antibodies. Our findings show that IgG of older DS patients (>30 years) binds to Torpedo cholinergic NF–H more readily than does that of young DS patients (<30 years) and age–matched normal controls. In contrast, the extent of binding of IgG from the young and older DS groups to Torpedo and bovine spinal cords NF–H is similar and equal to that of normal controls. These findings suggest that older DS patients, like AD patients, contain anti–NF–H IgG that binds specifically to epitopes highly enriched in Torpedo cholinergic NF–H.