Defective expression of c-Maf by Vav1-deficient T cells. CD4⁺ T cells from Vav1^–/– or wild-type mice were stimulated with plate-bound anti-CD3/CD28 antibodies under Th2- or Th1-inducing conditions. After 5 days, the cells were washed and restimulated in anti-CD3–coated plates. (A) RNA expression of c-Maf, T-bet, GATA-3, IL-4, IFN-γ, and IL-5 was analyzed at the indicated times by real-time RT-PCR. Transcript levels were normalized to the expression level of HPRT transcripts in the same sample and are represented as transcript abundance relative to unstimulated wild-type Th2 cells. The data shown are representative of 3 independent experiments. (B) Total lysates or nuclear extracts prepared 48 hours after restimulation were analyzed by immunoblotting with the indicated antibodies. Grb2 expression was analyzed as a control for equal protein loading. All data are expressed as the mean value of triplicate determinations ± SE.