Twist1 suppresses the expression of effector cytokines. DO11.10 Th cells were stimulated for 5 d under Th1- or Th2-polarizing conditions or without addition of cytokines. On d 2, cells were infected with control virus or twist1-encoding virus. The cells were restimulated on d 6 and stained for intracellular cytokine expression. (A) Representative histograms of cytokine expression in Th cells ectopically expressing twist1 (black line) and control cells (gray filled). The cells displayed were gated for expression of CD4 and the viral marker gene gfp. (B) Frequencies of cytokine-expressing cells among infected, i.e., GFP⁺CD4⁺ T cells relative to the noninfected CD4⁺ cells. Cells had been stimulated without addition of cytokines and infected with control virus (open bars) or twist1-encoding virus (filled bars). Data represent the mean ± SD of four independent experiments.