The in vivo Anti‐tumor Effect of Human Recombinant Interleukin‐6

Administration of recombinant interleukin-6 (IL-6) was found to induce in vivo generation of cytotoxic T lymphocytes (CTL) against syngeneic transplantable erythroleukemia (FBL-3) in lymph node cells and peritoneal exudate cells (PEC) in C57BL/6 mice. Furthermore, 15 out of 16 C57BL/6 mice injected with 5 x 10(6) viable FBL-3 cells survived on day 100 when they were treated with 5 x 10(4) U of recombinant IL-6 three times a day on days 1, 2, 3, 5, 7 and 9 after the inoculation of tumor cells (the cure rate was 94%). Cured mice could reject the tumor cells rapidly after the re-inoculation of a large number of live FBL-3 cells. In contrast, all normal mice died of tumor development by day 10. In these cured mice, FBL-3-specific CD4-8+ CTL cells were found to be generated in PEC, spleen and lymph node cells by either in vivo or in vitro re-stimulation with FBL-3 cells, but lymphokine-activated killer cells never developed. The results suggested that the anti-tumor effect of IL-6 was mediated by in vivo induction of tumor-specific CTL.