Tumor-bearing animals contain suppressed antitumor effectors the function of which can be unmasked by IL-2.
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 tumor-bearing 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.
Salvadori
S
S
Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029.
Rosenthal
F M
FM
Cronin
K
K
Gansbacher
B
B
Zier
K S
KS
D000818:Animals; D018106:CD28 Antigens / Q000276:immunology; D006084:Graft Rejection / Q000276:immunology*; D007108:Immune Tolerance; D007376:Interleukin-2 / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D013154:Spleen / Q000166:cytology / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D014407:Tumor Cells, Cultured
D018106:CD28 Antigens; D007376:Interleukin-2