A monoclonal antibody capable of detecting new differentiation antigen of the stomach

A monoclonal antibody (MAb) was raised against a gastric adenocarcinoma cell line TMK-1 that shows parietal cell differentiation. This MAb, an IgMK, named 20DII, reacted immunohistochemically with the intracytoplasmic secretory canalicular membranes of normal parietal cells of the stomach. In the fetal stomach at 4 months of gestation, the luminal surface of fundic epithelia and developing parietal cells had MAb20DII immunoreactivity, but at 6 months of gestation only parietal cells showed immunoreaction. Out of 133 gastric carcinomas, 98 (74%) had MAb20DII immunoreactivity. In the well-differentiated type, immunoreactivity was localized at the luminal surface of tumor cells and, in the poorly differentiated type, in the intracytoplasmic tubulovesicles of tumor cells. In Western-blot analysis, the antigenic molecule had a molecular weight exceeding 300 kDa in the tumor tissues, but only a 62-kDa immunoblot band was seen in the corresponding non-cancerous gastric mucosa. However, there was no correlation between the expression of high-molecular-weight antigens and the histological types of gastric carcinoma. These results suggest that 20DII antigen may be involved in differentiation of parietal cells in the fetal stomach and in stomach cancer.