AhR-deficient mice have impaired NK cell–mediated delayed CHS. (A) Schematic of CHS assay after T cell depletion. Mice were injected with 50 µg of anti-CD3–depleting antibody 1 d before sensitization with OXA. At 1 mo, mice were again injected with 50 µg anti-CD3 1 d before challenging with OXA by painting the ears. Ears were measured by micrometer, and ears were harvested 4 d after rechallenge. (B) Ear swelling of AhR^+/+ and AhR^−/− mice relative to control ears. Data are representative of two independent experimental cohorts, and n = 3–4 mice per group. (C) Representative H&E stains of OXA-challenged ears from AhR^+/+ (top) and AhR^−/− (bottom) mice at day 4 after rechallenge. (D) Schematic of adoptive transfer CHS assay. AhR^+/+ and AhR^−/− mice were sensitized with OXA, and 40,000 CD49a⁺DX5⁻ liver NK cells were adoptively transferred into B10;B6 Rag2^−/−γc^−/− mice. At 1 mo, mice were challenged with OXA by painting the ears. Ears were measured by micrometer, and ears were harvested 4 d after rechallenge. (E) Ear swelling of mice receiving 40,000 AhR^+/+ or AhR^−/− CD49a⁺DX5⁻ liver NK cells. n = 4–5 mice per group. (F) Representative H&E stains of OXA-challenged ears from AhR^+/+ and AhR^−/− recipient mice at day 4 after rechallenge. (C and F) Bars, 50 µm. Data are shown as mean ± SEM (two-way ANOVA).