Pulmonary histology of IL-18/IL-2–treated mice.

(A) Acute lethal effect. B6 mice were daily administered PBS alone (Ai) or a high dose of IL-18 (1 μg) plus 50 000 IU IL-2 (Aii-Aiii). Necropsy was performed after 2 (Aii) and 4 (Ai,Aiii) days of the treatment, and the lung tissue was microscopically observed with HE staining. Original magnification at the observation at × 200. (B) Chronic effect. B6 mice were daily administered a low dose of IL-18 (0.1 μg) plus 50 000 IU IL-2 (Biv-Bxii), PBS alone (Bi), IL-2 (50 000 IU) alone (Bii), or IL-18 (0.1 μg) alone (Biii), and were killed at the time point indicated (day 8, Biv-Bvi; day 18, Bvii-Bix; day 30, Bi-Biii; day 36, Bx-Bxii). The lung tissue was microscopically observed with HE (Bi-Biv,Bviii,Bx), Azan (Bv,Bviii,Bxi), or EVG (Bvi,Bix,Bxii) staining. Original magnification at the observation at × 200. (C) Morphology of the infiltrating cells. B6 mice were daily administered a high dose of IL-18 (1 μg) (Ci) or a low dose of IL-18 (0.1 μg) (Cii) plus 50 000 IU IL-2 for 4 and 36 days, respectively. The lung tissue was observed with HE staining. Foam cells (arrows) are present in the thick alveolar walls and general interstitium. Original magnification at the observation at × 400.