Human alpha-fetoprotein epitopes as revealed by monoclonal antibodies

The epitope specificity of 12 anti-human alpha-fetoprotein monoclonal antibodies (Mabs) was estimated in an enzyme-linked immunosorbent assay (ELISA). A combination of two different approaches: (i) Mabs binding to heterologous alpha-fetoprotein (AFP); and (ii) cooperative Mabs binding to human AFP (hAFP) when tested in pair mixtures; was used. This double-approach methodology was found to be more reliable for the definition of Mab specificities than either method alone. The anti-hAFP Mabs studied recognised eight unique non-repeated epitopes on hAFP. Two of the epitopes were specific for humans, whereas six were common to other species (mouse, rat, calf, dog, pig and cat) with a characteristic species distribution for each epitope. All epitopes were present on hAFP synthesised by hepatoma, yolk sac tumour and embryo.