The participation of antibody in spontaneous and antibody-dependent cell-mediated cytotoxicity in the pig

Treatment of porcine lymphocytes with trypsin reduced their spontaneous cell-mediated cytotoxicity (SCMC) activity against target cells persistently infected with transmissible gastroenteritis virus (PK15-TGE cells), but had no effect on antibody-dependent cell-mediated cytotoxicity (ADCC). SCMC activity was partially restored to trypsin-treated lymphocytes by incubation in RPMI-1640 medium or in medium containing F(ab')2 fragments of rabbit anti-porcine immunoglobulin, but not by brief incubation in autologous serum. F(ab')2 fragments of anti-porcine immunoglobulin did not block the SCMC reaction, but ADCC was greatly reduced by this reagent. Thus SCMC and ADCC mediated by porcine lymphocytes against PK15-TGE target cells clearly involved two distinct mechanisms in terms of antibody participation and sensitivity to trypsin.