Monoclonal antibodies against beta-human chorionic gonadotropin. A comparative immunohistochemical study

Eight choriocarcinomas and two immature placentas were stained with a polyclonal rabbit anti-beta-human chorionic gonadotropin (beta-hCG), a monoclonal mouse hybridoma anti-beta-hCG (MoAb1), and a monoclonal mouse hybridoma antibody that recognizes only a free beta-hCG chain (MoAb2). All stains were performed on neutral-buffered formaldehyde-fixed paraffin-embedded material using the avidin-biotin complex method. The polyclonal antiserum and MoAb1 stained all ten lesions. Syncytiotrophoblastic cells in all lesions, except one case of retroperitoneal choriocarcinoma, were stained with MoAb2. Absorption with intact beta-hCG inhibited staining by the polyclonal and MoAb1 antibodies, but failed to abolish staining with MoAb2. Absorption with purified free beta-hCG abolished the staining of all three antibodies, confirming that MoAb2 reacted only with free beta-hCG. These results indicate that these highly specific monoclonal antibodies can be used to detect various forms of beta-hCG in formaldehyde-fixed paraffin-embedded tissues.