Symposium: Cellular Immunity and the Immunotherapy of Cancer: Tolerance and Activation: PDF OnlySalvadori Silvia; Rosenthal, Felicia M.; Cronin, Kathryn; Gansbacher, Bernd; Zier, Karen S.Journal of Immunotherapy with Emphasis on Tumor Immunology: October 1993 Buy Abstract Summary CMS5 fibrosarcoma cells were infected with retroviral constructs containing interleukin-2 (IL-2) cDNA and selected in G418. Parental tumor cells and those that produced IL-2 were injected in vivo. Whereas injection of parental tumor cells resulted in progressive tumor growth, those secreting high levels of IL-2 were rejected. Furthermore, the immunosuppression associated with inoculation of parental tumor cells was not seen. To understand the failure of mice to reject non-IL-2-secreting tumor cells, functional responses of spleen cells from immune and tumor-bearing mice were studied in vitro. As expected, immune spleen cells proliferated under a variety of conditions but were inhibited in the presence of parental tumor cells. Even spleen cells from tumorbearing animals responded well in the absence of parental tumor cells or in the presence of parental tumor cells, if supplied with adequate levels of IL-2. These results suggest that both tumor-bearing and immune mice generate antitumor effectors but that the cells might be functionally suppressed because of their inability to secrete IL-2 after contact with parental tumor cells. © Lippincott-Raven Publishers.