THE INDUCTION OF CYTOTOXICITY BY A BISPECIFIC ANTIBODY AGAINST CEA POSITIVE CELL-LINE, IN-VITRO

A mouse anti-human carcinoembryonic antigen (CEA) x anti-human CD3 bis pecific antibody, AB5C10UCHT1, was developed. This antibody-heterocon jugate was chemically prepared by cross-linking the AB5C10 monoclonal antibody reactive with human CEA with the monoclonal antibody, UCHT1, which binds to CD3 on human T-lymphocytes. The AB5C10UCHT1 recognized both CEA expressed on the KATOIII cell fine and CD3 expressed on T-ly mphocytes, as determined using flowcytometry. Next, AB5C10UCHT1-media ted cytolysis was analyzed by Cr-51-release assay. When Cr-51-labeled target KATOIII cells were incubated for 6 h with effector cells that h ad been pretreated with AB(5)C(10)UCHT1 for 60 min at 4 degrees C, th e percentage specific lysis was significantly increased compared to th at of untreated effector cells. Using peripheral blood mononuclear cel ls (PBMC) and lymphokine-activated killer (LAK) cells pre-treated with AB5C10UCHT1 for effector cells, the percentage specific lysis was de termined to be 16.3% and 57.4% at effector:target (E:T) ratios of 100: 1 and 12.5:1, respectively. On the other hand, the percentage specific lysis of untreated PBMC and LAK cells determined to be 3.0% and 35.8% at E:T ratios of 100:1 and 12.5:1, respectively. The minimum effectiv e dose of AB5C10UCHT1 required for antibody-mediated cytotoxicity was 0.1 mu g/ml. The results of this study suggest that AB5C10UCHT1 coul d be useful for augmenting the cytotoxicity of CD3-positive T-cells ag ainst CEA-positive target cells in vitro.