Forced expression of A1 restores the survival of OX40 KO CD8 T cells in secondary responses in vitro.

Naïve CD8 cells from WT or OX40 KO OT-I TCR transgenic mice were stimulated with peptide and APCs. On day 2/3, T cells were transduced with retroviral vectors expressing GFP, or GFP with A1. On day 5 of primary culture, GFP⁺ CD8 T cells were sorted, and restimulated with APCs and peptide. (a) Recall survival, based on recovery of GFP⁺Vβ5⁺ T cells over time. Cell numbers present on day 0 were assigned a value of 100%, and cell numbers surviving on day 2, day 4 and day 6 were used to calculate the percentage recovery. Data represent the mean ± s.d. percentage changes from three separate experiments (p>0.05). (b) Recall IL-2 and IFN-γ production by ELISA at 40 h. Data are means ± s.d. from three experiments (p>0.05).