Figure 3.

Culture in IL-15 reduces downregulation of transgene expression

Healthy donor T cells were activated, transduced with lentivirus (pLVX-1383I, left) or retrovirus (SAMEN-1383I, RV, right), then CD34-sorted and rapidly expanded. (A) Lentiviral- and retroviral-transduced T cells were then cultured in the presence or absence of IL-2 and IL-15. Expression of CD34 and Vβ12 was assessed by flow cytometry on CD4⁺ or CD8⁺ CD3⁺ T cells at indicated time points. (B) Lentiviral- and retroviral-transduced T cells were cultured for 14 days in the absence or presence of T2 cells, T2 cells pulsed with tyrosinase, 624 MEL cells, or IL-2 (300 IU/mL) and IL-15 (100 ng/mL). Tumor cells were added at a ratio of 1:4 tumor:T cell. On day 12, tumor cells were no longer detectable, and a second dose of tumor cells was added. Error bars represent standard deviation. Significance is shown by Student’s t test with p values summarized as ∗∗p < 0.01, and ∗p < 0.05.