Inhibition of Lymp hocyte - ADC C by A - Neutrophils Cells

Human neutrophils, activated by phorbol-myristate acetate (PMA). (A-neutrophils), were found to suppress lymphocytic killer (K) cell-mediated antibody-dependent cellular cytotoxicity (ADCC). Resting (R) neutrophils, ie, PMAuntreated cells, were completely ineffective. Suppression was optimal when A-neutrophils were added at the beginning of the ADCC assay. Furthermore, A-neutrophils were found to cause an approximately 80% reduction in the number of Raji target cell-bound lymphocytes. These data indicate that A-neutrophils inhibit K cell activity by interfering with the target cell recognition. A-neutrophils were capable of reducing the percentage of Fc receptor (FcR)bearing lymphocytes with a half-time of 7.2 minutes, through a process preventable by the serine-protease inhibitors tosyl-lysine-chloromethyl ketone (TICK) and lima bean trypsin inhibitor (IBTI). Conversely. A-neutro-