Automatic and simultaneous analysis of Lens culinaris agglutinin-reactive alpha-fetoprotein ratio and total alpha-fetoprotein concentration.

An automated analytical method for analyzing alpha-fetoprotein (AFP) carbohydrate chain microheterogeneity based on competitive reaction between lectin and anti-AFP monoclonal antibody in liquid phase is described. The antibody used binds to all species of AFP molecule without Lens culinaris agglutinin (LCA); however, its binding reaction to LCA-reactive AFP was inhibited by LCA. Sulfated tyrosine octamer was conjugated to the antibody, and sulfated tyrosine pentamer and peroxidase were conjugated to other monoclonal antibodies, respectively. Serum reacted with three anti-AFP monoclonal antibodies and LCA in liquid phases, and two types of immune complex were observed. The two types were separated directly by the liquid-phase binding assay system equipped with an anion-exchange column. Peroxidase activity of immune complex was determined fluorophotometrically. Total AFP concentration and the ratio of LCA-reactive AFP in samples were calculated simultaneously, using the sum of the two peaks and the ratio of peaks obtained by LCA inhibition to sum of two peaks. The results correlated well with conventional methods. The method is simple and convenient for routine clinical assays.