Rsk2 is required for the early phase of T-cell proliferation and expression of IL-2 but is not required for IFNγ and IL-4 production. (A) Purified T cells isolated from WT and Rsk2 KO (KO) mice were labeled with CFSE and stimulated with plate-bound anti-CD3 (2 μg/mL) plus anti-CD28 (1 μg/mL). The rates of cell division for CD4⁺ and CD8⁺ T cells were determined by dilution of CFSE on days 2 and 3, respectively. Representative flow cytometric profiles are shown and the percentage of cells undergoing cell division is indicated. (B) Summary of the CFSE experiment for data derived from days 2 to 4. Shown is the mean plus or minus SEM (WT: n = 3; KO: n = 4). (C) Purified T cells from WT and Rsk2 KO mice were stimulated using 2 μg/mL plate-bound anti-CD3 plus 1 μg/mL anti-CD28 for 24 hours, and the cells were stained first with anti-CD4 APC or anti-CD8 APC and then with 7AAD and Annexin V–PE. Apoptotic cells were indicated as 7AAD⁺/Annexin V⁺ cells. (D) Shown are data from 3 independent experiments. Error bars represent SEM.