The Use of Monoclonal Antibodies to Define Levels of Cystatin C in Normal Human Serum

Abstract

We established four hybridoma cell lines which secreted monoclonal antibodies against human cystatin C. These monoclonal antibodies were of IgA(κ), IgG_2a(λ), IgG₁(κ), and IgG₁(λ) isotypes, respectively. The association constants (K_a) of the three IgG monoclonal antibodies ranged from 3.6 x 10⁹ M^-1 to 7.3 x 10¹⁰ M^-1. An ELISA technique for the measurement of cystatin C was established by using one of these monoclonal antibodies. The assay procedure was highly specific, sensitive, and reproducible. The lower detectable limit of cystatin C by this procedure was 1.9 ng/ml. The level of cystatin C in normal human serum was 1.16 ± 0.91 μg/ml (mean ± S.D., n=274).