Extrinsic factors affect the differentiation of TRAF6-deficient Th17 cells. CD4⁺ T cells isolated from TRAF6-ΔT and congenic (CD45.1) wild-type mice were stimulated alone or mixed at 1:10 and 10:1 ratios (Mix) under Th17-skewing conditions. After 4 days of culture, cells were restimulated and stained for flow cytometric analysis. Numbers in flow cytometry plots indicate percentages of IL-17–expressing CD4⁺ T cells. Right panel represents results from triplicate wells in 1 of 2 experiments. Lines represent average values of the triplicate wells. *P < .05 (unpaired analysis), **P < .05 (paired analysis).