Enhanced cytokine production by IL-4Rα KO CD8⁺ T cells. (A) Bulk CD8⁺ T cells from WT and IL-4Rα KO were stimulated with plate-immobilized anti-CD3 and anti-CD28 for 6 or 24 h and stained for intracellular TNF or IFN-γ. (B–D) WT and IL-4Rα KO CD8⁺ T cells were sorted into the subsets indicated and then stimulated with anti-CD3 and anti-CD28 for 6 (B and C) or 24 h (D) before intracellular staining for TNF (B) or IFN-γ (C and D). Error bars indicate mean ± SD. P-values are represented as *, P < 0.05; **, P < 0.01; ****, P < 0.0001 by unpaired Student’s t test. n = 4 for WT and n = 4 for IL-4Rα KO for each graph, and data are representative of three (A) or two (B–D) experiments.