BCG induced killer cell activity.

To investigate the mechanism of Bacillus de Calmette Guérin (BCG) bladder instillation therapy, the killer cell activity induced in peripheral blood mononuclear cells (PBMNCs) after BCG instillation was examined. Significant cytotoxic activity against natural killer (NK) cell resistant target tumor cells was detected after 3 days of instillation. To characterize this BCG induced cytotoxic activity further, human PBMNCs were cultured with BCG in vitro. From 24 h maximum cytotoxicity was obtained and continued for 3 days, then decreased slightly. Neither a DNA synthesis inhibitor Cytosine-arabinoside (Ara-C) nor a cytotoxic T cell (CTL) generation inhibitor Cyclosporine A inhibited this killer cell activation. Monoclonal antibody treatment revealed that both precursor and effector cells are Leu1-, 3a-, 7+, 11b+. The recognition specificity from cold target competition experiments was selective. Taken together NK type precursor was activated with BCG into NK type effector which has wider spectrum of target cells than usual NK cell.