OX40 is dispensable for T cell proliferation and direct antiviral T cell function.

(A) WT and OX40−/− P14 cells were labeled with CFSE prior to injection in WT recipients. Graph is showing CFSE dilution of congenically marked TCR transgenic (WT red, OX40−/− black) and unlabeled endogenous CD8 T cells (grey area) 5 days post infection. (B, C) CD45.1/2 mismatched WT and OX40−/− TCRtg cells were co-transferred into WT recipients prior to LCMV cl13 infection and BrdU was injected intraperitoneally on day 6 post infection according to the manufacturer's instructions. Cells were harvested and BrdU staining was detected by flow cytometry to visualize cells that had proliferated. Data are representative for 1 out of 2 independent experiments. (D) Intracellular cytokine staining (ICCS) for IFN-γ, IL-21 and IL-2 was performed 10 days post infection following peptide stimulation (n = 5 per group). (E) Representative FACS-plots showing IFN-γ and IL-21 production of WT, Het and KO smtg cells. (F) Intracellular cytokine staining (ICCS) for IFN-γ following GP33 peptide stimulation on congenically marked TCR transgenic CD8 T cells (P14) transferred into WT recipients was performed 5 and 8 days post infection (n = 4–5 per group). Data are derived from 2 independent CD4 smtg cell transfer experiments and 2 independent CD8 P14 cell transfer experiments.