Histopathological changes of mice ear lesion. Each sample was obtained 24 h after the fifth application and fixed with 10% neutral formalin. Sections were stained with hematoxylin and eosin (× 200). (A) vehicle-treated wild type BALB/c mice, (B) DNFB-treated wild type BALB/c mice, (C) vehicle-treated IL-4 gene-depleted BALB/c mice, (D) DNFB-treated IL-4 gene-depleted BALB/c mice, (E) Vehicle-treated wild type C57BL/6 mice, (F) DNFB-treated wild type C57BL/6 mice, (G) Vehicle-treated IL-4 gene-depleted C57BL/6 mice, (H) DNFB treated IL-4-depleted C57BL/6 mice.