Antibody-dependent and spontaneous cell-mediated cytotoxicity against transmissible gastroenteritis virus infected cells by lymphocytes from sows, fetuses and neonatal piglets

The ontogeny in the pig of effector lymphocytes mediating antibody-dependent and spontaneous cell-mediated cytotoxicity against target cells infected with transmissible gastroenteritis virus was investigated. The same activities were also studied in sows in late pregnancy and early lactation. Peripheral blood lymphocytes and intraepithelial lymphocytes collected from piglets during the first week of life failed to mediate cytolysis as determined by chromium release assays, but significant activities developed during the second week and usually increased further by the sixth week. Peripheral blood lymphocytes collected from fetuses on the 109th gestation day failed to produce spontaneous cell-mediated cytotoxicity and only reacted in antibody-dependent cell-mediated cytotoxicity when contaminated with macrophages. The cytotoxic activities of peripheral blood lymphocytes from sows were lowest at parturition. It was concluded that impaired lymphocyte cytotoxicity in newborn piglets and parturient sows may contribute to their relatively high susceptibility to transmissible gastroenteritis.