Summary
A peptide, Gly-Pro-Arg-Val-Val-Glu, corresponding to the first six residues of the
amino terminus of the a-chain of human fibrin (desAA-fihrin) was prepared by solid-phase
peptide synthesis. The peptide was covalently linked to keyhole-limpet hemocyanin
(KLH) and used as an immunogen for preparing monoclonal antibodies. A monoclonal antibody
specific to the hexapeptide, but not to KLH or fibrinogen, was produced. The antibody
did not bind to thrombin-mediated clots prepared from either plasma or purified fibrinogen.
However, immunoreactivity was detected when fibrin (prepared from fibrinogen) was
solubilized with 8 M urea. In contrast, a monoclonal antibody specific to the amino
terminus (Gly-His-Arg-Pro-Leu-Asp-Lys) of the (β-chain of fibrin recognized the epitope
in clots. These results indicate that thrombin cleavage of fibrinogen produces a structural
change in the amino terminal domain of the α-chain that makes it inaccessible to antibody
interaction. In addition, our study suggests that the potential clinical application
of monoclonal antibodies to localize fibrin-rich thrombi must take into account the
final structure of clots.
