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 × 10(6) viable FBL‐3 cells survived on day 100 when they were treated with 5 × 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.