We investigated the existence of antibodies in sera of Alzheimer's dis
ease patients which immunoreact with specific antigens from crude huma
n brain extracts. We found that 49% of patients, per only 5% of contro
l subjects, had increased levels of antibodies to a 240 kDa protein. O
n the basis of immunological criteria and internal aminoacid sequencin
g, this antigen was identified as brain spectrin, a cytoskeletal prote
in which appears to be implicated in synaptic plasticity. Our data rai
ses the possibility that anti-spectrin antibodies could be implicated
in Alzheimer's disease pathogenesis.