Monoclonal Antibodies to the Amino- and Carboxyl-Terminal Domains of Human Transferrin

Abstract

Seven high affinity antibodies to human serum transferrin which recognize at least four different epitopes are described. Apparent dissociation constants (K_d's) have been determined for the binding of the antibodies to human transferrin in the presence and absence of iron. Small differences in reactivity were found. Five of the antibodies bind to the isolated amino-terminal half-molecule of human transferrin. Two of the antibodies appear to be to the C-terminal lobe since they bind to holo-transferrin but do not recognize the N-terminal half-molecule. Immunoblotting shows that six of the antibodies recognize both reduced and nonreduced transferrin. In addition, all of the antibodies bind with sufficiently high avidity to transferrin to make them useful as probes in studies in which binding of transferrin to the specific transferrin receptor is examined.