Demonstration of cross-reacting material in Tay–Sachs disease

Abstract

Antibodies against placental hexosaminidase A and kidney α-subunits were raised in rabbits after cross-linking the antigens with glutaraldehyde. Anti-(αn-subunit) antiserum (anti-αn) precipitated hexosaminidase A but not hexosaminidase B, whereas anti-(hexosaminidase A) antiserum precipitated both hexosaminidases A and B. Specific anti-(hexosaminidase A) antiserum was prepared by absorbing antiserum with hexosaminidase B. Both anti-αn and anti-(hexosaminidase A) antisera precipitated the CR (cross-reacting) material from eight unrelated patients with Tay–Sachs disease. Immunotitration, immunoelectrophoresis, double-immunodiffusion and radial-immunodiffusion techniques were used to demonstrate the presence of CR material. The CR-material–antibody complex was enzymically inactive. Antiserum raised against kidney or placental hexosaminidase A, without cross-linking with glutaraldehyde, failed to precipitate the CR material, implying that treatment of the protein with glutaraldehyde exposes antigenic determinants that are hidden in the native protein. Since anti-(hexosaminidase B) antiserum did not precipitate the CR material during the immunoelectrophoresis of Tay–Sachs liver extracts, it is suggested that altered α-subunits do not combine with β-subunits. By using immunotitration we have demonstrated the competition between the hexosaminidase B-free Tay–Sachs liver extract and hexosaminidase A for the common binding sites on monospecific anti-(cross-linked hexosaminidase A) antiserum. The amount of CR material in the liver samples from seven cases of Tay–Sachs desease was found to be in the same range as theoretically calculated α-subunits in normal liver samples. Similar results were obtained by the radial-immunodiffusion studies. The present studies therefore suggest that Tay–Sachs disease is caused by a structural-gene mutation.