[Specific quantification of gamma-seminoprotein-alpha 1 antichymotrypsin complex in serum by monoclonal antibody-based enzyme immunoassay].

Gamma-seminoprotein (gamma-Sm) is one of the serine proteinases in seminal plasma, and is well known as a tumor marker of prostate cancer. In the blood, a major portion of gamma-Sm combines with alpha 1 antichymotrypsin (ACT), a serine proteinase inhibitor. We developed a sensitive enzyme immunoassay (EIA) for the gamma-Sm-ACT complex using two different monoclonal antibodies (MoAbs). One MoAb, prepared against gamma-Sm, is used for the capture, and the other, prepared against ACT, is conjugated with horseradish peroxidase and used for detection. The detectable range of this assay in clinical applications was from 0.2 to 50 units/ml. The intra-assay coefficients of variation (CV%) obtained from ten repeated assays of three sera were 3.6 to 5.5%. The mean gamma-Sm-ACT complex concentration in the sera of normal individuals was determined to be 0.86 +/- 0.11 units/ml for males (n = 50) and 0.11 +/- 0.08 units/ml for females (n = 54). There was no significant increase in the level of the complex with increasing age in males. The ratio of the gamma-Sm-ACT complex to free gamma-Sm tended to be significantly higher in patients with prostate cancer than in those with benign prostatic hyperplasia.