A panel of monoclonal antibodies to ovine placental lactogen

A panel of 11 rat monoclonal antibodies (mAbs) has been raised to ovine pla cental lactogen (PL). By competitive enzyme-linked immunoabsorbent assay (E LISA), confirmed by two-site ELISA, the antibodies were shown to recognize six antigenic determinants on the ovine PL molecule, two of which overlap. One antigenic determinant (designated 1) was shared by other members of the : prolactin/growth hormone (GH)/PL family in ruminants, humans and rodents. The binding of I-125-labelled ovine PL to crude receptor preparations from sheep liver (somatotrophic) or rabbit mammary gland (lactogenic) was inhib ited by mAbs recognizing antigenic determinants 2-6. Both types of receptor preparation were affected similarly. In the local in vivo pigeon crop sac assay, mAbs directed against determinants 3 and 6 enhanced the biological a ctivity of ovine PL.