Differential effect of IL-2, IL-7, IL-15, and IL-21 gene transfer on tumor-specific human T-cell proliferation and Bcl-2 expression. (A) Proliferation of transduced T cells in response to mitogenic stimulation. On day 7 after AAPC stimulation, 19z1⁺ T cells were purified, labeled with CFSE (2μM), and stimulated with plate-bound anti-CD3 (10 μg/mL) and soluble anti-CD28 (1 μg/mL) antibodies. At 3 and 8 days later, T cells were analyzed for CFSE dilution of the CD4⁺ and CD8⁺ subsets. One of 2 donors is shown with similar results observed in both. (B) Bcl-2 expression by transduced T cells. On day 7 after AAPC stimulation, T cells were assessed for expression of Bcl-2 protein by flow cytometry. Histograms are representative of 4 donors and have been gated on 19z1⁺CD4⁺ or 19z1⁺CD8⁺ T cells. The bar graph depicts Bcl-2 MFI (± SEM) of 19z1⁺CD4⁺ or 19z1⁺CD8⁺ cells from 4 donors that has been normalized such that the MFI of Bcl-2 for the 19z1-ΔLNGFR group = 1. *P < .05, **P < .01, #P < .005 versus 19z1-ΔLNGFR.