The splenocytes prepared as described above were adjusted to a final density of 5 × 106/mL, and stimulated with or without Con A (5 μg/mL) and LPS (10 μg/mL), respectively. The cells were incubated in 96 well plates at 37 °C in an incubator with 5% CO2 for 48 h. Lymphocyte proliferation was assessed by the absorbance at 570 nm through following MTT assay.