Monoclonal antibodies to rabbit progesterone receptor: crossreaction with other mammalian progesterone receptors.

Abstract

A mouse was immunized with purified rabbit uterine cytosolic progesterone receptor (specific activity:3 nmol of steroid bound/mg protein). After fusion of its spleen cells with mouse Sp2-OAg myeloma cells, supernatants of 11 hybrid cultures reacted in both an immunoenzymatic test and a double-immunoprecipitation test with the progesterone receptor. Clones were obtained from the 5 hybrid cells that gave the strongest response in both tests. Antibodies from cell culture supernatants and ascitic fluids were characterized. Three are of the IgG1 and 2 of the IgG2a isotype. Their apparent affinity for the progesterone receptor was measured by immunoprecipitation in physiological salt conditions. The equilibrium dissociation constants were between 0.1 and 4 nM. All 5-monoclonal antibodies crossreacted with the rabbit nuclear receptor, the human cytosolic receptor and other mammalian (rat and guinea pig), but not avian (chicken) cytosolic progesterone receptors. There was no interaction with glucocorticoid receptor and corticosteroid binding globulin.