Development of a monoclonal antibody to the rabbit 8.5S uterine progestin receptor

Nonactivated (8.5S) rabbit uterine progestin receptor was enriched 10- to 30-fold by chromatography on columns of spheroidal hydroxylapatite and DEAE-cellulose. A total of approximately 25 micrograms of receptor (purity approximately 1%) was injected at multiple sites into a BALB/c mouse. After several injections, splenic lymphocytes were fused with P3x63Ag8.653 mouse myeloma cells. This fusion produced in excess of 240 hybridomas, which were screened by an enzyme-linked immunosorbent assay (ELISA), solid-phase radioimmunoassay, and sucrose gradient centrifugation. One colony (KN 382/EC1) produced a mouse immunoglobulin G1 which bound rabbit 8.5S uterine progestin receptor. The cell line has been repeatedly cloned under conditions of limiting dilution and expanded in mice as ascitic tumors. Antibody was purified by (NH4)2SO4 precipitation, DEAE-cellulose chromatography, and affinity chromatography with protein A - Sepharose CL-4B. Specificity of the antibody was determined by sucrose gradient centrifugation and solid-phase radioimmunoassay. The antibody bound to progestin receptors from rabbit uterus and MCF-7 breast cancer cells. It did not react with progestin receptors from rat uterus, guinea pig uterus, or chick oviduct, nor did it bind to estrogen receptors from any of the tissues we tested.