Monoclonal antibodies against estrogen receptor: interaction with different molecular forms and functions of the receptor.

Hybridoma cells have been produced by fusing SP2/O-Ag14 mouse myeloma cells with spleen cells from a mouse immunized with a purified preparation of estrogen receptor from calf uterus. The antibodies, all of the immunoglobulin G (IgG) class, interact with different forms of calf receptor as well as with rat and human receptors. The equilibrium dissociation constant of the antibody-receptor complex was measured in solid phase and in solution. With immobilized antibodies the Kd is 0.06 nM whereas in solution it is 0.5 nM. Only one antigenic determinant is present per molecule of receptor with the antibodies tested. The antibodies JS34/32 are able to form only a 1:1 complex with the 8S form of the receptor, whereas a 2:1 receptor-IgG complex is formed at low antibody concentration with the high-salt or nuclear form of receptor. The antibodies JS34/32 and JS28/32 prevent neither the nuclear uptake of the receptor nor the extraction of the translocated receptor from the nuclei.