PURPOSE: To obtain a human chorionic gonadotropin (hCG) highly specific antibody by forming the same in such a way as not to have cross reactivity with the other hypophysis celebri hormones such as human luteinizing hormone (LH), human follicule-stimulating hormone (FSH) and thyroid-stimulating hormone (TSH).

CONSTITUTION: This anti hCG specific monoclonal antibody is obtd. in the following way: Hybridoma is first obtd. by the cell fusion of the spleen cells of the BALB/C mouse immunized by hCG and mouse myeloma cells (P3UI). The antibodies which do not cross with the other hypophysis celebri hormones such as LH are screened by executing screening of the hybridoma by simple autoradiography. Absence of crossing with the α chain and β chain of hCG is further confirmed by autoradiography. The clone subjected to the above-mentioned process is thereafter cultured and the intended monoclonal antibody is obtd. from the culture supernatant thereof.