Fig. 4

Role of IFNγ in triggering apoptosis of tumor-specific CD8⁺ T cells. a Quantitative RT-PCR analysis of IFNγ mRNA expression in induced TiRP tumor tissues collected 4 days after ACT. Results normalized to β-actin are expressed relative to the level measured in control tumors that did not receive ACT (controls: n = 20; ACT: n = 24). b Fresh homogenates from induced tumors collected 4 days after ACT were cultured in vitro for 24 h and supernatants were tested by ELISA for the presence of IFNγ (controls: n = 22; ACT: n = 34). c Tumor-bearing mice received 0.5 mg neutralizing anti-IFNγ antibody i.p. 1 day before transfer of activated TCRP1A CD8⁺ T cells. Four days after transfer, dissociated tumor tissues were analyzed ex vivo by FACS for apoptosis of TCRP1A CD8⁺ T cells (controls: n = 23; anti-IFNγ: n = 9). d Quantitative RT-PCR analysis of FasL mRNA expression in induced TiRP tumor tissues collected 4 days after transfer of activated TCRP1A CD8⁺ T cells preceded or not by injection of neutralizing anti-IFNγ antibody as in a–c. Results normalized to β-actin mRNA level are expressed relative to the level measured in control tumors that did not receive TCRP1A CD8⁺ T-cell transfer (controls: n = 12; T-cell transfer: n = 11; T-cell transfer + anti-IFNγ: n = 8). e Quantitative RT-PCR analysis of FasL mRNA expression in induced TiRP tumor tissues (n = 19) as compared with T429.11 transplanted tumor tissues (n = 14). Results normalized to Gapdh are expressed relative to the level measured in transplanted tumors. Results are expressed as mean ± s.e.m. Unpaired t-test, two-tailed, *P < 0.05, **P < 0.01, ***P < 0.001. ****P < 0.0001