Abstract
The influence of interleukin 2 (IL2) on the cytotoxic activity of lymphocytes from patients with melanoma against autologous and a variety of allogeneic melanoma cells was studied. IL2 was produced from blood lymphocytes cultured for 24 h with phytohaemagglutinin (PHA) and purified by membrane chromatography to exclude PHA. Lymphocytes from 13 patients with melanoma at various clinical stages were cultured for 6 days with IL2 (2 U/ml) and then tested for cytotoxic activity against autologous melanoma cells, three allogeneic melanoma and three non‐melanoma cells. Autologous cytotoxicity was generated by culture with IL2 alone and was not increased by culture with both IL2 and autologous tumour cells. Marked increases in cytotoxic activity were also generated against the allogeneic target cells and were maximal against the NK‐insensitive Chang target cells. Similar degrees of cytotoxicity were induced by IL2 stimulation of lymphocytes from melanoma patients, patients with non‐melanoma carcinoma and normal subjects against the allogeneic target cells. Cold target inhibition studies were carried out against IL2 induced autologous cytotoxicity in five patients. In four of five studies the autologous target cells inhibited more than the allogeneic target cells. There was no significant difference between the inhibition produced by allogeneic melanoma cells and that produced by non‐melanoma cells. Similarly, in studies against allogeneic target cells, there was no significant difference in the inhibition produced by allogeneic melanoma compared to non‐melanoma target cells. This applied irrespective of whether effector cells were from melanoma or non‐melanoma subjects. These results suggest that lymphocytes from patients with melanoma are primed against autologous antigens in vivo and that provision of a second signal, IL2, in vitro can induce cytotoxicity against the autologous tumour. The cytotoxicity generated against the allogeneic target cells did not appear to have specificity to melanoma. Several results, such as the pattern of cytotoxicity against the target cells and changes in cell surface markers on the lymphocytes during culture, suggested that cytotoxicity was mediated by activated T cells rather than by natural killer cells. These findings appear to have important implications both in the understanding of tumour host relationships and for the use of IL2 in therapy.