Human lymphocyte and monocyte lysis of tumor cells mediated by a mouse/human IgG1 chimeric monoclonal antibody.

The mouse monoclonal antibody 17-1A (gamma 2a, kappa) recognizes a tumor-associated antigen expressed on human gastrointestinal malignancies and has been used in Phase I and II clinical trials. Chimeric genetic constructs have been produced using 17-1A variable region genes (VL and VH) and the constant region genes for human kappa light chains and gamma 1 heavy chains (C kappa and gamma 1). The chimeric gene constructs were transfected into mouse myeloma cells for antibody production. The secreted mouse/human chimeric antibody contains the antigen-binding domain of 17-1A and the human (gamma 1, kappa) constant regions. Native mouse 17-1A and the chimeric antibody (chIgG1) were analyzed for binding to two human colon cancer cell lines and for the mediation of cancer cell line antibody-dependent cellular cytotoxicity by normal human peripheral blood lymphocytes and monocytes in 4 h 51Cr-release assays. The 17-1A and chIgG1 gave similar results in these in vitro biologic assays. This study demonstrates the feasibility of using mouse/human chimeric antibodies in human therapeutic applications.