ANTIBODIES TO ESTROPHILIN - COMPARISON BETWEEN RABBIT AND GOAT ANTISERA

The immunochemical similarity of mammalian estrophilins has been demonstrated by the ability of immunoglobulin (Ig-i) obtained from rabbits and a goat immunized with purified estradiol-receptor complex of calf uterine nuclei to cross-react with all radioactive estradiol-receptor complexes (E*R) tested to date, as determined by sucrose gradient, gel filtration and double antibody precipitation techniques. Rabbit antibodies to the nuclear receptor of calf uterus react with 5.2 S nuclear E*R from calf, rat, rabbit and sheep uterus, as well as from rat endometrial and pituitary tumors to give two more rapidly sedimenting E*R-Ig-i complexes (7-8 S and 10-12 S). Extranuclear E*R (4 S) from uteri and tumors of several mammalian species, and from rat and human mammary cancers, as well as nuclear and extranuclear E*R (3.5 S) from MCF-7 human breast tumor cells, give a single major sedimentation peak (7-8 S) with rabbit Ig-i. The hormone specificity of rabbit Ig-i has been demonstrated by the absence of any interaction between Ig-i and androgen receptors of rat prostate, or mammalian and non-mammalian progesterone receptors. Also, there is no reaction with free estradiol, with non-specific binding components in human breast cancer cytosol, or with 125I-labeled mouse or rat a-fetoprotein. Goat antibodies to calf uterine E*R react with nuclear and extranuclear E*R of all tested tissues, including uterus, tumor and human breast cancer, to give a major new entity sedimenting at 11-14 S. The titer of antibodies to estrophilin in goat Ig-i is considerably higher than in rabbit Ig-i. Unlike rabbit antibody, interaction of goat Ig-i with extranuclear estrophilin causes a decrease in affinity and a reduction in the number of binding sites for estradiol. Fab fragments from both rabbit and goat Ig-i react with nuclear E*R from calf uterus to give a product sedimenting slightly ahead of the original E*R complex. © 1979.