Monoclonal antibodies against the androgen receptor: recognition of human and other mammalian androgen receptors.

Overview

abstract

Monoclonal antibodies against the androgen receptor (AR) will provide useful probes for elucidating both the structure and function of this important regulatory protein. Recently, human autoimmune anti-AR sera have been described. The purpose of the current work was to immortalize lymphocytes from the blood of patients with high titer anti-AR antibodies and to produce monoclonal antibodies against the receptor in vitro. Human serum samples (10 microliters) were incubated in high ionic strength buffer (400 mM KCl) for 16 h at 0 C with [3H]Mibolerone-labeled cytosol (100-200 fmol AR) from Dunning tumors. Receptor-antibody complexes were precipitated with goat antihuman immunoglobulin (Ig) antibody. From our 1005 serum samples examined, 5 specimens were detected which precipitated greater than 40% of the AR. These antibodies recognized the AR from human, rat, mouse, dog, steer, chicken, and hamster, but did not recognize estrogen, progesterone, or glucocorticoid receptors. By sucrose gradient analysis in high salt (0.4 M KCl) 1 of the antisera shifted the 4.4S monomeric receptor to 8S, and the others shifted the receptor to 18S. However, all of the antibodies were shown to be IgG class by immunoprecipitation with class-specific second antibodies. Peripheral blood lymphocytes donated by these patients were isolated by histopaque density gradient sedimentation, activated in vitro, transformed with Epstein-Barr virus, and seeded into 96-well plates. From 263 million human lymphocytes plated in 96-well dishes, 1215 wells gave rise to Epstein-Barr virus-transformed lymphoblastoid cells, and 8 of these wells were determined to be anti-AR positive. Cells from 2 of the positive wells were cloned and designated CB54 and UA67, both of which secreted IgG class antibodies against the AR. These 2 monoclonal antibodies have been shown to be highly specific for the AR and to cross-react with the AR from human, rat, and hamster. Studies with the monomeric form of the AR and its proteolytic fragment using sucrose density gradients have suggested that the 2 antibodies recognize different epitopes on the monomeric AR molecule. Furthermore, by Western blot analysis the antibodies have identified the AR as an 118K protein on a sodium dodecyl sulfate gel, which is consistent with our previous findings of the mol wt of the AR.