A Cancer‐reactive Human Monoclonal Antibody Derived from a Colonic Cancer Patient Treated with Local Immunotherapy

A human monoclonal antibody, YJ‐37 (IgM) was generated through the fusion of human B lymphoblastoid cell line HO‐323 with the regional lymph node lymphocytes from a colonic cancer patient who was treated with a local immunotherapy. This antibody was purified and conjugated with biotin, after which direct immunohistochemical staining was performed. The results revealed that YJ‐37 selectively reacted with colonic cancer (7/19), gastric cancer (3/6), endometrial cancer (1/2) and colonic adenoma (7/13), but not with normal epithelia. Membrane immunofluorescence and FACS analysis also showed that YJ‐37 bound to tumor cell surfaces. Furthermore, the chemical structure of the antigen defined by YJ‐37 was analyzed by means of thin‐layer chromatography immunostaining and ELISA. The results indicated that YJ‐37 reacted with sialylated lacto‐series carbohydrate chains, which have been reported to accumulate in cancer cells.