Figure 3. IFN-γ independence of T-bet's anti-proliferation activity. CD4⁺ Th cells were isolated from IFN-γ KO mice and IFN-γ/T-bet double KO mice and stimulated with anti-CD3 in the either presence (+) or absence (-) of exogenous rhIL-2. Cells were cultured for an additional 2 to 3 days under Th1-skewing (A) or Th2-skewing (B) conditions. Cell proliferation rates of developing Th cells from either T-bet WT or T-bet KO mice established IFN-γ-deficient background were determined using a thymidine incorporation assay. A total of 5 mice per group were used for analysis and data are expressed as the average ±SD. ^**p<0.005, ^***p<0.0005.