Apoptosis and necrosis of splenic lymphocytes 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 collected. The spleens were prepared as cell suspensions as described in the Materials and Methods and then incubated with FITC and PI. Spleen lymphocyte necrosis (PI+) and apoptosis (FITC+PI+) were assayed with a flow cytometer (FCM) (A1-A2). Data are presented as the mean ± SD, n = 6 for each group (B1-B2). *Significant difference between the PG treatment and SM exposure groups (*P < 0.05, **P < 0.01, ***P < 0.001).