Transfer of TRAF1-expressing memory T cells enhances viral control. WT P14 or TRAF1^−/− P14 splenocytes were stimulated with GP33 peptide, and then washed and incubated with IL-15 for 6 d to generate memory like T cells as described in the Materials and methods. (a) Western blot analysis of TRAF1 levels in P14.TRAF1^−/− and P14.WT T cells before transfer, compared with TRAF1 levels in LCMV tetramer⁺ (GP33, GP276, and NP396) CD8 T cells sorted from LCMV clone 13–infected mice at day 21 after infection (labeled as d21.tet⁺ in blot). (b and c) Mice were infected with 2 × 10⁶ PFU/mouse LCMV clone 13. On day 21 post-infection, one million in-vitro-generated memory P14.WT or P14.TRAF1^−/− T cells were transferred via the intravenous route. Mice were sacrificed 14 d later for analysis of T cells and viral titers. (b) Representative FACS plots are shown for GP33-specific CD8 T cell function as measured by production of IFN-γ and TNF in response to GP33 peptide restimulation as outlined in Materials and methods. Similar results were observed in three mice. In a separate and independent experiment, a higher percentage of GP33-tetramer⁺ CD8 T cells were found in P14.WT-transferred mice as compared with the P14.TRAF1^−/−-transferred mice or mice without transfer. (c) Viral titer in kidney at 2 wk after P14 T cell transfer. Data are pooled from two independent experiments with a total of six mice without transfer, five mice with P14.WT transfer, and five mice with P14.TRAF1^−/− transfer.