Dynamic changes of the spleen lymphocyte proliferation 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 prepared in a cell suspension as described in the Materials and Methods, with resulting spleen lymphocytes suspended in RPMI 1640 with 10% FBS and Concanavalin A (Con A) (0.5 μg/ml). At 56 h after Con A stimulation, 10 μl 3H-TdR was added to each slot. Spleen lymphocyte proliferation was assayed by measuring the 3H-TdR of the original proliferation (RPMI 1640) (A) and T lymphocytes (Con A) (B) described in Section 2. The proliferation ratio of the control group was set to 1.0, and data were presented as the fold increases compared with their respective vehicle controls. *Significant difference between the PG treatment and SM exposure group (*P < 0.05, **P < 0.01, ***P < 0.001). Data were presented as the mean ± SD, n = 6 in each group (A-B).