Characterization of a monoclonal antibody to human alpha-fetoprotein and its use in affinity chromatography.

A hybrid cell line secreting monoclonal antibodies to human alpha- fetoprotein (AFP) was produced by fusion of a mouse myeloma cell line with spleen cells from a BALB/c mouse immunized with human AFP. The affinity constant of the antibody was about 1.7 X 10(9) l/mol. When clones were grown in vitro, the highest concentration of specific antibody in the culture medium was 25 microgram/ml. A clone was transplanted intraperitoneally into pristine-primed BALB/c recipients. Ascites developed within 3-4 weeks of transplantation, and the maximal antibody concentration in the ascitic fluid was 2.5 mg/ml. The immunoglobulin fraction of ascitic fluid was coupled to cyanogen bromide-activated Sepharose and used for affinity chromatography of AFP. AFP containing less than 1% contaminating proteins was obtained by passing amniotic fluid through the column and eluting the adsorbed AFP with 4 mol/l urea. The monoclonal antibody was used for radioimmunoassay (RIA). The sensitivity obtained was 50 microgram/l, which is adequate for certain clinical applications.