YFP⁺ T cells in cKO mice exhibit reduced expansion in response to LCMV infection. cKO and cHet mice were treated with tamoxifen and infected with LCMV-Arm 5 days later. Splenocytes were examined 8 days after infection. (A) The frequency of CD8 T cells in the YFP⁺ (left panel) and YFP⁻ (right panel) splenocyte populations was determined. (B) Splenocytes were restimulated with the indicated peptides and the frequency of IFNγ-producing YFP⁺ (left panel) and YFP⁻ (right panel) CD8 T cells was determined by intracellular staining. (C) The frequency of LCMV-specific YFP⁺ CD8 T cells was determined using tetramers. A representative flow cytometry plot is shown and all graphs represent the means ± SD of at least 4 mice.