Rsk2 is required for optimal IL-2 expression but not for IL-4 and IFNγ expression and Th1 and Th2 differentiation. (A,B) Shown are IL-2 mRNA (A) and protein (B) induction in T cells from WT and Rsk2 KO (KO) mice stimulated by anti-CD3, anti-CD3 plus anti-CD28 (A), and anti-CD3 plus anti-CD28 (B). For IL-2 protein production, equal volumes of supernatants collected from same number of cells were used for enzyme-linked immunosorbent assay (ELISA). The error bars display the standard error of mean (n = 9 for panel C and n = 3 for panel D). (C,D) Shown are a representative experiment for IL-4 mRNA (C) and IFNγ mRNA (D) expression stimulated by anti-CD3 plus anti-CD28 in T cells from WT and Rsk2 KO (KO) mice. Shown are the means plus or minus SEM (n = 3). (E) Purified CD4⁺ T cells from either WT or Rsk2 KO mice were polarized to Th1 and Th2 cells and expanded for a total of 6 days before overnight restimulation with anti-CD3 plus anti-CD28. Expression of IFNγ and IL-4 in Th1 and Th2 cells stimulated by anti-CD3 plus anti-CD28 was determined by intracellular staining. Representative flow cytometric profiles are shown, and the percentages of Th1 cells expressing IFNγ and of Th2 cells expressing IL-4 are indicated.