The 7-day cumulative survival rate of mice in the CLP group was significantly lower than that in the Sham group (30.00% vs. 100.00%; Log-Rank test χ 2 = 47.470, P < 0.001), and the peripheral blood inflammatory mediators TNF-α, IL-12 and IL-4 were increased 24 hours after operation, followed by a significant decreasing at 48 hours, and then gradually increased at 72 hours. IFN-γ gradually increased 24 hours after operation and lasted for 72 hours. Immunohistochemistry showed that a large number of C5aR was expressed in pulmonary and renal endothelial cells 48 hours after operation in the CLP group. Compared with the Sham group, the proportion of DC [(1.80±0.30)% vs. (6.90±1.20)%, P < 0.05] and Treg [(0.38±0.02)% vs. (4.00±0.50)%, P < 0.05] in splenic mononuclear cells was down-regulated in the CLP group, the proportion of Th17 was up-regulated [(0.83±0.08)% vs. (0.32±0.03)%, P < 0.05], and disorder of immune function was found. After anti-C5A monoclonal antibody intervention, the 7-day cumulative survival rate increased significantly compared with the CLP group (54.54% vs. 30.00%; Log-Rank test χ 2 = 28.090, P < 0.001); TNF-α, IL-12 and IFN-γ were further increased, while IL-4 was significantly decreased; the expression of C5aR in lung and kidneytissues were significantly decreased, and the expression of mature DC cells [(5.10±1.20)% vs. (1.80±0.30)%, P < 0.05] and Treg [(2.58±0.05)% vs. (0.38±0.02)%, P < 0.05] in spleen were significantly increased compared with the CLP group, and Th17 was significantly decreased [(0.54±0.05)% vs. (0.83±0.08)%, P < 0.05].