Characteristics of antibodies to calmodulin in patients with Graves' disease.

We detected an antibody to calmodulin (CaM) in sera from patients with Graves' disease. Four sera out of 300 from patients with Graves' disease demonstrated increased CaM binding activity as compared with 300 sera from normal subjects, while no binding activity was detected in sera from autoimmune thyroiditis. The binding could be demonstrated as due to the antibody to CaM by the double antibody method, polyethyleneglycol method, gel filtration and radioimmunoelectrophoresis, respectively. These antibodies were thought to be polyclonal immunoglobulins (IgG and/or IgA). CaM has proven to be a poor antigen because of the structural identity of CaM from different species. The incidence of the antibody to CaM in Graves' disease is low and the pathophysiological significance of this antibody to CaM had remains obscure.