Fig. 1

Cytological analysis of BALF after intratracheal instillation of NiO NPs, NiCl₂, and OVA. NiO NPs were instilled at 200 cm²/rat and cytological evaluation was performed at 1, 2, 3, and 4 days after instillation. NiCl₂ was instilled at 378.0 μg/rat, which is equivalent to the nickel dose (171.1 μg Ni/rat) of NiO NPs at 200 cm²/rat, and cytological evaluation was performed at 1 day after instillation. a, Number of total cells. b Number of macrophages. c Number of neutrophils. d Number of eosinophils. Abbreviations: VEH, vehicle control for NiO NPs and NiCl₂; OVA, ovalbumin-induced allergic airway inflammation; VEH_OVA, vehicle control for OVA group. Mean ± SEM (n = 10 for NiO NPs and n = 4 for NiCl₂ and OVA group). One-way ANOVA test was applied for comparison between NiO NPs and VEH with statistical significance indicated by ^* p < 0.05, ^** p < 0.01, and ^*** p < 0.001. Student’s t-test was applied for comparison of NiCl₂ against VEH and OVA group against VEH_OVA with statistical significance indicated by ^## p < 0.01 and ^### p < 0.001