Recombinant interleukin-2 inhibits growth of human tumor xenografts in congenitally athymic mice.

Administration of human recombinant interleukin-2 (RIL-2) into congenitally athymic (nu/nu) mice carrying subcutaneous transplants of HeLa, HU 609T and T24B human carcinoma cells partially inhibited growth of the human tumor xenografts. In vitro activation of nu/nu spleen cells with human RIL-2 resulted in generation of killer cells showing in the 51Cr cytotoxicity assay similar levels of cytolysis as RIL-2-activated spleen cells from heterozygous (nu/+) mice. The RIL-2-activated (LAK) cells were cytotoxic for a variety of mouse and human tumors, reaching the peak of their cytotoxic activity after 3 days of cultivation in the RIL-2-containing medium. The cytotoxic activity of activated nu/nu spleen cells was significantly reduced by treatment with antibody against glycolipid asialo GM1, the differentiation antigen of natural killer (NK) cells. This finding suggests that in addition to the conventional, asialo GM1- LAK cells, asialo GM1+ activated NK cells participated in the cytotoxicity displayed by the IL-2-activated nu/nu killer spleen cells.