Monoclonal antibody against human growth hormone receptor.

GHR shows a high degree of homology with the prolactin receptor and with the other receptors that belong to the hemopoietic receptor superfamily. This paper describes a monoclonal antibody (MAb) (2B4B6) specific for both the extracellular domain of human GHR and human growth hormone (GH) binding protein. Mice were immunized against a seven-aminoacid peptide sequence screened by FASTA (sequence similarity search served by Genome-Net) from the European Bioinformatics Institute to exclude the existence of human membrane proteins with significant sequence homology. MAbs were screened against the peptide sequence and 2B4B6 was selected for its capability to recognize the full-length hGHBP. As evaluated by both enzyme-linked immunoadsorbent assay (ELISA) and FACS analysis, this MAb seems to recognize and bind to a hGHR positive cell line, IM-9, as well as a murine cell line, BaF3 (8/6), transfected with a chimeric construct, hGHR/hG-CSFR and expressing hGHR on the cell membrane. Studies investigating the biological effects of this MAb showed that anti-hGHR mediated inhibition of cell proliferation was not due to competition with GH binding but rather to prevention of receptor dimerization. Because of its specificity, this MAb may be usefully applied in situations in which GHR and receptors with a high degree of homology, such as PRLR (prolactin receptor), are expressed simultaneously, as occurs in the immune system.