Ability of Specific Monoclonal Antibodies and Conventional Antisera Conjugated to Hematoporphyrin to Label and Kill Selected Cell Lines Subsequent to Light Activation

A variety of cell lines have been prepared by fusion of the murine WEH1 3B cell line with peripheral blood leukocytes from a patient with chronic granulocytic leukemia. Fusion products were selected for their ability to produce a leukemia-associated antigen (CAMAL) previously described. One such line which originally produced CAMAL subsequently lost this ability and was used as a negative control. A number of antibodies were conjugated to hematoporphyrin (HP) and tested for their ability to bind to cell lines as detected by either fluorescence or by their ability to kill cells after light activation. The antibodies used were: rabbit anti-Hu (a conventional rabbit antiserum raised to membrane preparations from normal human peripheral blood leukocytes which served as a positive control); CAMAL-1 (a monoclonal γ1 antibody with specificity for the CAMAL antigen); and L1210 (an irrelevant monoclonal γ1 antibody). HP was conjugated to the antibodies by a carbodiimide procedure. When labeled cells were examined by fluorescence microscopy, it was apparent that both the rabbit antibody and CAMAL-1:HP showed positive labeling. The ability of the antibody:HP conjugates to kill labeled cells following light activation was tested. It was shown that rabbit anti-Hu:HP and CAMAL-1:HP conjugates were capable of killing significant numbers of cells when HP concentrations were as low as 1.2 ng/106 cells, whereas similarly treated cells exposed to either L1210:HP or HP alone did not exhibit significant killing until concentrations reached 240 and 120 ng/106 cells, respectively. Further experiments in which other cell lines were tested, all at HP concentrations of 12 ng/106 cells, demonstrated that those lines producing CAMAL were killed, whereas negative lines were not.