Direct and indirect effects of T-bet on selectin ligand induction. (A) Enforced overexpression of T-bet in WT Th0 cells fails to induce maximal levels of selectin ligands. WT CD4⁺ T cells were activated under Th0 conditions, infected with retroviruses (RVs) expressing no cDNA (empty) or T-bet, and cultured under Th0 conditions. Cells were then stained with P- or E-selectin chimeras or 1B11. Uninfected WT Th1 cells were included side-by-side for comparison. Numbers given for retrovirally transduced cells are the percentage of the GFP⁺ cells which stain for either 1B11 (first column), P-selectin ligands (second column), or E-selectin ligands (third column). One representative of 3 similar experiments. (B) T-bet deficiency inhibits functional expression of the IL12R. WT and T-bet^-/- CD4 cells were cultured under Th1 conditions for 6 days, washed, and restimulated with IL-12. At the indicated time points, cells were harvested, lysed, and subjected to Western blotting for tyrosine phosphorylated, and total Stat4. Results are representative of 2 experiments. KO indicates knock-out.