Human Monoclonal Antibodies against Cytokeratin 18 Generated from Patients with Gastric Cancer

By co‐culturing regional lymph node B‐cells and HAT‐sensitive mutant cells obtained from RPMI‐1788 cells, no less than 20,000 Epstein‐Barr (EB)‐transformed colonies were obtained from 32 patients with gastric cancer. From B‐cell cultures generating antibodies reactive with gastric cancer tissues as well as cultured gastric cancer cells, two EB‐transformed cell clones termed C418–59 and C1218–39 were isolated. Both of them produced human IgM‐class antibodies, termed Mab418–59 and Mab 1218–39, respectively. Both antibodies reacted with an antigen with a molecular weight of 45 kd existing in gastric cancer MKN‐45, MKN‐1, and Kato‐III cells, and also with all of 4 adenocarcinomas of the stomach in paraffin sections. The antigen recognized by both antibodies was identified as a kind of cytoskeletal protein, cytokeratin 18, In this study, it was confirmed that B‐cell clones generating autoantibodies against cytokeratin 18 were present in some patients with gastric cancer.