PURPOSE: To make it possible to obtain a medicine, etc., useful for treating cancer-related diseases, etc., by administering a specific protein as an antigen into an animal body, separating and preparing cells of the animal.

CONSTITUTION: A peptide corresponding to an amino acid sequence within an N-terminal region of a protein belonging to a protein group (36K family) having about 36000 molecular weight in membrane proteins is chemically synthesized and a desired carrier is bound to afford an antigen, which is then mixed with Freund's complete adjuvant and administered into the abdominal cavity of a mouse, etc., 2-4 times at an interval of about 2 weeks. Cells of a spleen, etc.) extracted from the resultant immunized animal are then mixed with myelomatous cells at (1.10):1 ratio and subsequently cultured in an HAT culture medium containing thymidine, etc., to provide fused cells. The obtained cells are then administered, cultured into ascitic fluid of a mouse, etc., and subsequently purified by chromatography, etc., to produce a monoclonal antibody, which is then used to identify or determine a protein belonging to the 36K family.