Histology
At 3 days after CLP challenge[21], mice were sacrificed by CO2 inhalation. Then, the spleens were collected and fixed in 4% paraformaldehyde solution for more than 48 hours before being embedded in paraffin and sectioned. After deparaffinization and rehydration, the sections were stained with hematoxylin and eosin (H&E). The congestion and necrosis of the spleen tissue and the aggregation of inflammatory cells were evaluated under an optical microscope. Then the spleen injury scores of mice based on the results of H&E[23] was evaluated by two independent, blinded researchers.