A screening assay for monoclonal antibodies based on the availability of a polyclonal antiserum

A double-sandwich enzyme-linked immunospecific assay (ELISA) has been developed for screening hybridoma clones for monoclonal antibodies against human alpha-fetoprotein (AFP). The assay uses commercial polyclonal antiserum to bind alpha-fetoprotein from biological fluids, and the complex then binds the specific monoclonal antibodies in hybridoma culture supernatants. The sandwich is completed with commercial peroxidase-linked anti-mouse immunoglobulin. In exploring the variables of this system, it was found that the quality of the polyclonal anti-alpha-fetoprotein antiserum was the most critical factor. The assay functioned with as little as 10 ng alpha-fetoprotein from cord serum or amniotic fluid. A variety of commercial peroxidase-linked second antibodies was satisfactory, and both IgG and IgA class monoclonals were detected. Comparison of the ELISA with a standard radioimmunoassay showed the former to perform very adequately as a general hybridoma screening assay.