Priming with transforming growth factor-β (TGF-β) leads to decreased GATA-3 and increased T-bet expression. Purified CD4+ T cells from DO11.10 transgenic mice (a–f) were cultured with ovalbumin (OVA), antigen-presenting cells (APC), interleukin (IL)-2 (a–d), IL-12 + anti-IL-4 (a), IL-4 + anti-IL-12 + anti-interferon-γ (IFN-γ)(b), anti-IL-12(c), or anti-IL-12 + TGF-β(d)for 1 week. Cells were subsequently restimulated with immobilized anti-CD3 (a–d) and analysed by fluorescence-activated cell sorting (FACS) for intracellular IL-4 and IFN-γ. Numbers reflect the percentage of CD4+ T cells secreting cytokine. cDNA made from cells in (c) was subjected to real-time polymerase chain reaction (PCR) using both GATA-3 and T-bet-specific primers, and the expression of GATA-3(e)and T-bet(f)was determined. Expression is reported as relative units compared to 18s expression. Th1, T helper 1; Th2, T helper 2.