Epitope Mapping of Human Luteinizing Hormone Using Monoclonal Antibodies

To establish structure-function relationships for human (h) LH, 14 murine monoclonal antibodies (MABs) to hLH were characterized in terms of their affinity of binding (Ka), their specificity for intact glycoproteins and their subunits, their paratopic relationships, and their ability to interfere with the biological activity of hLH. The Ka values obtained ranged between 2.4 × 106 and 1.0 × 1010 for intact hLH and between 2.3 × 106 and 7.5 × 108 liters/M for the free α- and β-subunits, indicating that, in general, the antibodies showed higher avidity for the intact hormone. Six MAB recognized both the intact and free α-subunit of hLH, cross-reacted with intact hCG, hFSH, and hTSH, and thus appeared to be a-directed. Four MAB were β-directed, recognizing both intact hLH and its free β-subunit. One of these β-directed MABs also cross-reacted with intact hCG, hFSH, and hTSH, while two others recognized both intact and free β-subunits of hLH and hCG. The fourth β-directed MAB was quite specific for intact hLH ...