Control of human melanoma growth in nude mice by autologous allo-activated peripheral blood lymphocytes

Human peripheral blood lymphocytes (PBL) were activated in vitro by means of a pool of allogeneic PBL from normal donors and then evaluated for in vivo activity against human melanoma cells xenografted in splenectomized and irradiated athymic (nude) mice. The subcutaneous (s.c.) growth of human melanoma cells was inhibited by intravenous (i.v.) injection, 2 hr later, of such allo-activated, autologous and allogeneic PBL in 7/8 and in 6/9 mice respectively. Unstimulated PBL were ineffective. When allo-activated patients' lymphocytes were administered 3 days after s.c. implantation of autologous melanoma cells, inhibition of tumor growth was observed in 1/6 mice. A significant delay in tumor appearance was noted in the remaining animals. Unstimulated as well as allo-activated, lymphokine-releasing helper-enriched human PBL had no effect on melanoma xenografts, indicating that the tumor inhibition by tumor-cytotoxic allo-activated PBL was not due to recruitment of murine immuno-competent cells by human lymphokines. These results indicate that allo-stimulated tumor-cytotoxic human PBL given i.v. to nude mice can circulate and inhibit the growth of autologous or allogeneic human melanoma cells implanted s.c.