Natural killer (NK) activity of porcine blood lymphocytes against allogeneic melanoma target cells

Allogeneic PM/86 melanoma cells of Munich Troll miniature swine have been used for the demonstration of porcine peripheral blood NK cell activity. Compared with the specific lysis of xenogeneic K562-, U937- and Vero-target cells, NK cell-mediated cytotoxicity (NK-CMC) against PM/86 melanoma tumor cells was significantly lower in a 16 h chromium release assay. The target cell susceptibility to peripheral blood NK-CMC of both adult Troll miniature swine and German Landrace sows was very similar. Cold target inhibition assays revealed the allogeneic PM/86 melanoma cells to be the most powerful inhibitors of NK-CMC. Nylon wool non-adherent lymphocytes produced interferon (IFN)-alpha in different quantities upon contact with NK susceptible target cells. The NK effector cells could be stimulated to a higher lytic activity against all susceptible targets by a moderate dose of natural human interleukin-2 (nhuIL-2). The role of NK-CMC in melanoma tumor rejection and/or prevention of metastases is yet unknown in swine although porcine melanoma serves as a good model for the disease in man.