The use of monoclonal antibodies to distinguish several chemically modified forms of human α₁-proteinase inhibitor

The purpose of our investigation was to obtain monoclonal antibodies that could distinguish three forms of α 1-proteinase inhibitor (α 1-PI): native α 1-PI, N-chlorosuccinimide-oxidized α 1-PI (Ox-α 1-PI) and proteolytically modified α 1-PI (α 1-PI). Three specific monoclonal antibodies were characterized as to their binding properties. By using the Bio-Dot assay, it was found that all three forms of α 1-PI were capable of binding to antibody 6D4-6-18, that only Ox-α 1-PI, but not native α 1-PI or α 1-PI, could bind to antibody 6C7-5, and that α 1-PI and a complex between α 1-PI and trypsin uniquely were not able to bind to antibody 5C12-8-7. Thus it was concluded that it is possible to use monoclonal antibodies with different epitopic specificities to distinguish two chemically modified forms of α 1-PI from the native protein.