Generation of tumor cell-reactive human monoclonal antibodies using peripheral blood lymphocytes from actively immunized colorectal carcinoma patients.

The use of human monoclonal antibodies (MCA) in the detection and treatment of human cancer has been limited by the apparent scarcity of MCA to tumor cell surface antigens. Using peripheral blood lymphocytes from autologous tumor-immunized patients, we isolated 36 MCA that react to sections of colorectal carcinoma. Twenty of these human MCA appear to be directed against cell surface antigens. Two-thirds of the human MCA-producing cell lines were diploid human B-cells rather than human-mouse heterohybridomas. Direct antibody-binding assays performed with the MCA indicated that they recognized antigenic determinants preferentially expressed on tumor cells. Experiments with paired specimens of air-dried, dissociated colon tumor cells and normal colonic mucosa cells suggested that the MCA bound significantly more to the cell surfaces of tumor cells than to the surfaces of normal colonic mucosa cells. Similarly, tests with a panel of cryostat sections of paired colon tumor and normal colonic mucosa showed that MCA bound to the tumor cells and not to the normal colonic mucosa. None of the MCA bound to cells from frozen sections of normal breast, stomach, liver, skeletal muscle, or skin. Furthermore, the human MCA did not react with carcinoembryonic antigen and human erythrocyte antigens as measured by various techniques. Our data also demonstrated that these transformed B-cells and hybridomas were stable producers of human MCA. Thus, our studies show that these tumor-specific human MCA may have the specificity and stability necessary for in vivo evaluation of their use in the detection and treatment of cancer.