A heat stable serum inhibitor of an antigen antibody reaction of subacute sclerosing panencephalitis.

A factor which inhibits the antigen antibody reaction was isolated from the sera of patients affected with subacute sclerosing panencephalitis (SSPE), multiple sclerosis (MS) and also of control subjects. This factor inhibits the immune reaction between SSPE serum IgGs and measles virus. This inhibiting factor was detected in the alpha globulin region after agar gel electrophoresis, and is heat stable at 100 degrees C for ten minutes.