Performance of multistep immunochemical reactions by counterflow isotachophoresis on nitrocellulose membranes--II. Epitope analysis of monoclonal antibodies.

The method for comparison of epitope specificity of different monoclonal antibodies to one antigen, using a panel of monoclonal antibodies to mouse and human alpha-fetoprotein is described. The method used exploits the special properties of electroendosmotic flow in nitrocellulose membranes under the conditions of anionic isotachophoresis. Electroendosmosis allows successive transfer of several immunoreagents to the dots of monoclonals previously bound to the nitrocellulose membrane. The inhibition of antigen binding to monoclonal dot, if the antigen is mixed with excess of another monoclonal antibody, demonstrates that both monoclonals are directed to the same epitope, and vice versa. The method requires neither purified monoclonals nor antigens, or radio labelling, and is performed semi-automatically. It was shown that each monoclonal antibody to mouse and human alpha-fetoprotein had its own epitope specificity.