Abstract
An enzyme immunoassay method using a monoclonal antibody for the determination of 11-deoxycortisol is described. The anti-11-deoxycortisol antibody was produced in ascites by inoculating antibody-secreting hybridoma cells into BALB/c mice. The enzyme labeling of 11-deoxycortisol was carried out by the N-succinimidyl ester method. The activated esters of three carboxylated steroids were treated with β-galactosidase to give enzyme-labeled antigens. A protein A-double antibody method was employed for separation of the bound and free fractions in the immunoassay. It.was found that the monoclonal antibody had a high affinity for a homologous enzyme-labeled antigen prepared from 4- (2-carboxyethylthio) -11-deoxycortisol and the binding was inhibited by the analyte, 11-deoxycortisol. In the heterologous systems using labels prepared from 11-deoxycortisol 3- (O-carboxymethyl) oxime and 11-deoxycortisol 21-hemisuccinate, a lower and no significant immunoreactivities were observed, respectively. These results indicate that the antigen-binding site of the monoclonal antibody is complementary to and covers the 11-deoxycortisol portion remote from the position used for attachment to, the carrier in the preparation of the immunogen. The homologous assay system showed high sensitivity and specificity comparable to those of the radioimmunoassay using tritium as a tracer. These findings should be helpful in the development of various immunoassay systems with the monoclonal antibody.
