Sensitive enzyme immunoassay for human Mn superoxide dismutase.

A sensitive sandwich-type enzyme immunoassay for measurement of human Mn superoxide dismutase (Mn SOD) was developed using purified antibodies specific to Mn SOD. The antisera were raised in rabbits by injecting Mn SOD purified from human liver. The antibody IgG, purified by the use of Mn SOD-coupled Sepharose, showed a single band on the immunoblotting test with a crude liver extract. The assay system consisted of polystyrene balls with immobilized monospecific antibody F(ab')2 fragments and the same antibody Fab' fragments labeled with beta-D-galactosidase from Escherichia coli. The assay was highly sensitive and the minimum detection limit was 1 pg human Mn SOD/assay tube. Serum Mn SOD concentrations of healthy adults (77.5 +/- 18.0 ng/ml (1 SD), n = 120, 16-64 yr old) were not related to age or sex. Immunoreactive Mn SOD was detectable in most tissues examined except for erythrocytes. The concentrations of immunoreactive Mn SOD and Cu/Zn SOD in the cerebral cortex were not different among the patients with Alzheimer's disease, and the age matched and young patients without neurological disorders.