Dynamic decrease in the spleen weight and organ coefficient of the spleen in mice exposed to sulfur mustard (SM). Male KM mice were exposed to saline, propylene glycol (PG) and 20 mg/kg SM by subcutaneous injection. Six animals from each group were sacrificed after SM exposure at 4 h, 24 h, 72 h and 168 h, and the spleens were quickly weighed. The spleen weight (A) and organ coefficient of the spleen (B) of every animal were observed to assess SM-induced immune organ injury. Data were presented as the mean ± SD, n = 6 in each group (A-B). *Significant difference between the PG treatment and SM exposure groups (*P < 0.05, **P < 0.01, ***P < 0.001).