[Effects of serum immunosuppressive factors on the cytotoxicity of lymphokine-activated killer (LAK) cells induced by recombinant interleukin 2(R-IL2)].

Fundamental studies were performed on adoptive immunotherapy, especially on effects on lymphocytic cytotoxic activity, of nonspecific immunosuppressive factors (ferritin, IAP, AFP) and of serum factors obtained from gastric cancer patients, and possible intervention of suppressor T cells in serum immunosuppressive activity on the cytotoxicity was also examined. The following results were obtained. 1) Cytotoxicity of LAK cells induced by culturing normal peripheral blood lymphocytes (PBL) with R-IL2 in the medium containing normal AB-type sera, was higher than that of PBL. 2) Effect of nonspecific immunosuppressive factors on cytotoxicity of LAK cells was lower than that on cytotoxicity of PBL. 3) Cytotoxicity of PBL was inhibited in a relatively specific fashion by sera from patients of the cancers which were of identical histological types with the target tumor cells, while that of LAK cells was hardly inhibited by patients' sera. 4) Cytotoxicity of Leu 15-PBL was inhibited by nonspecific immunosuppressive factors and also by cancer patients' sera in a relatively specific fashion in relation to histology. 5) Cytotoxicity of Leu 15-LAK cells was hardly inhibited by serum nonspecific and specific immunosuppressive factors. The above results showed that serum immunosuppressive factors might act on PBL cytotoxicity without intervention of suppressor T cells, and that LAK cells were hardly inhibited by such immunosuppressive factors. All these results suggested usefulness of adoptive immunotherapy with LAK.