Monoclonal antibodies to estrophilin: probes for the study of estrogen receptors.

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Abstract
Splenic lymphocytes from a Lewis rat, immunized with purified estradiol-receptor complex of calf uterine nuclei, were fused with cells of 3 different mouse myeloma lines (P3-X63-Ag8, P3-NSI/I-Ag4-I and Sp2/0-Ag14) to yield hybridoma cultures, 9% of which produced antibodies to the receptor protein (estrophilin). When cloned by limiting dilution, .apprx. 70% of the viable cultures secreted antiestrophilin antibody. When expanded in suspension culture, 3 clones derived from Sp2/0-Ag14 secreted rat IgG (.gamma.2a class), whereas 7 other clones (from all 3 myeloma lines) secreted IgM. Monoclonal IgG shows comparable affinity for nuclear and extranuclear receptors, whereas IgM reacts preferentially with the nuclear form. Both classes of antibody react with unoccupied and with occupied receptor and do not interfere with its ability to bind to estradiol. By growing IgG-secreting clones in the presence of [35S]methionine, radiolabeled monoclonal antiestrophilin was prepared. Unlike antiestrophilin antibody previously generated in the rabbit or the goat, which crossreacts with estrogen receptors from every animal species tested, antibodies produced by the Lewis rat and by hybridomas derived from its spleen cells react specifically with estrophilin from calf tissues. These monoclonal antibodies provide reagents for the application of immunochemical techniques to study estrogen receptors in calf target tissues.