Monoclonal antibody to the hen oviduct progesterone receptor produced following in vitro immunization

The progesterone receptor of the hen oviduct is composed of two non-identical hormone-binding polypeptide subunits, A (Mr = 79,000) and B (Mr = 108,000). We used a highly purified preparation of B to immunize mouse spleen cells in vitro. After 5 days in culture, the cells were fused with SP2/0-Ag 14 myeloma cells. The resultant hybridomas were screened using an enzyme linked immunosorbent solid phase assay, and those hybridomas producing antibodies binding to the immunogen were cloned by limiting dilution. One such clone, 9B3-12, secreted an antibody of immunoglobulin class IgM, which binds to B. This was indicated by the ability of the antibody to increase the rate of sedimentation coefficient of the B subunit. Further, when the proteins in the B preparation were separated by electrophoresis and blotted onto nitrocellulose filters the antibody bound to a protein of 108,000 daltons. The antibody produced by 9B3-12 also reacted with subunit A and with the human progesterone receptor but failed to bind to the chick liver glucocorticoid receptor or to progesterone in the absence of its receptor.