Monoclonal antibodies to the rat liver glucocorticoid receptor

Monoclonal antibodies against the 90 000 mol. wt. form of the activated rat liver glucocorticoid receptor were generated from mice immunized with a partially purified receptor preparation. The screening assay was based on the precipitation of liver cytosol, labelled with [3H]triamcinolone acetonide, with monoclonal antibodies bound to immobilized rabbit anti-mouse IgG. Out of 102 hybridomas obtained, 76 produced immunoglobulin and eight of them were found to react with the receptor molecule. Only one of the positive clones secreted IgG whereas the other seven produced IgM. The complexes of receptor and antibodies were identified by sucrose density gradient centrifugation. All seven monoclonal antibodies tested reacted with the 90 000 mol. wt. form of the receptor but not with the 40 000 mol. wt. form that contains the steroid and DNA binding domains. None of the monoclonal antibodies interfered with the binding of the receptor to DNA cellulose, thus suggesting that the antigenic determinants are located in a region of the receptor that is not directly implicated in either steroid binding or DNA binding. These antigenic determinants were common to glucocorticoid receptors from several tissues of the rat, whereas glucocorticoid receptors from other species react only with some of the antibodies.