The preparation of an ovine monoclonal antibody to progesterone

Peripheral blood mononuclear cells were collected from a sheep immunized against progesterone-11 alpha-hemisuccinate-ovalbumin. Following fusion with NS1 mouse myeloma or heteromyeloma cells, a large number of hybrid colonies was established. These were screened for the production of sheep antibodies to progesterone. Twenty-four cell lines were cloned and one was stabilized. This cell line, O/MP.1A9.D7B2, produced a high-affinity ovine immunoglobulin G1 (dissociation constant 4.8 pmol/l) with a high degree of specificity for progesterone. The antibody was substituted into a competitive enzyme-linked immunosorbent assay for the measurement of progesterone in bovine milk, originally established using an ovine polyclonal antibody, and the results were compared. The monoclonal antibody produced an assay with a lower limit of detection and a greater degree of discrimination than the polyclonal antiserum.