Inhibition of Human Melanoma Growth in Nude Mice by Autologous, Alloactivated Peripheral Blood Lymphocytes

Peripheral blood lymphocytes of melanoma patients were stimulated in vitro by a pool of allogeneic lymphocytes and shown to be cytotoxic against autologous melanoma cells. To evaluate the in vivo antitumor activity of the cytotoxic alloactivated autologous peripheral blood lymphocytes, tumor neutralization (Winn) assay was carried out by injecting such lymphocytes admixed with autologous melanoma cells in athymic BALB/c nude mice. In 3 of 6 cases, complete inhibition of tumor growth was obtained at lymphocytes to tumor cells ratio of 10:1 and in one case also of 5:1. In all cases the appearance of tumors was delayed and the growth rate was significantly reduced in a dose-dependent fashion as compared to control mice injected with tumor cells alone. We conclude that in vitro alloactivated peripheral blood lymphocytes can inhibit and/or impair the growth of autologous melanoma cells in nude mice.