关键词: 多房棘球蚴, 原头节, 髓源抑制性细胞, 细胞因子

Abstract:

Objective To analyze the dynamic changes in the proportion of myeloid-derived suppressor cells (MDSCs) and their subtypes in peripheral blood leukocytes of mice infected with Echinococcus multilocularis protoscoleces and detect the expression of cytokines related to MDSCs proliferation in the late-infected mice serum. Methods Twenty-four BALB/c mice were randomly divided into the infected group and the control group, with 12 mice in each group. Mice in the infected group were intraperitoneally injected with 1 200 E. multilocularis protoscoleces, while mice in the control group injected with the same volume of normal saline. Three mice from each group were randomly selected at 30, 90 and 180 days after infection to observe histomorphological changes in liver and spleen. Peripheral blood was collected from orbital venous plexus to prepare peripheral blood leukocytes. After incubation with externally labeled antibodies to CD11b, Gr-1, Ly6G and Ly6C, flow cytometry was used to detect the proportions of MDSCs, polymorphonuclear MDSCs (PMN-MDSCs) and monocytic MDSCs (M-MDSCs). Serum samples from both groups were collected 180 days after infection for determine the concentrations of interleukin-6 (IL-6), IL-13, tumor necrosis factor α (TNF-α) and granulocyte-macrophage colony-stimulating factor (GM-CSF) by ELISA assay. GraphPad Prism 9.0 software was utilized for graphical and statistical analysis; independent sample t-test was used for inter-group comparison. Results After E. multilocularis protoscoleces infection, cysts appeared in the liver of infected group mice 30 days after infection, and volume of cysts was increased over time. Spleen of infected group mice were enlaged over time 30, 90, and 180 days after infection. The results of flow cytometry showed that 30, 90 and 180 days after infection, the proportion of MDSCs in peripheral blood leukocytes of infected group were (13.2 ± 2.4)%, (15.7 ± 2.3)% and (41.3 ± 4.0)%, respectively. And the proportion of MDSCs in the control group were (12.4 ± 3.2)%, (6.0 ± 0.9)% and (22.3 ± 1.1)%, respectively. The infected group was significantly higher than the control group 90 and 180 days after infection (t = 3.949, 4.682; P < 0.05, 0.01). 30, 90 and 180 days after infection, the proportion of PMN-MDSCs in peripheral blood leukocytes of infected mice were (10.9 ± 2.1)%, (12.5 ± 2.4)% and (35.8 ± 3.6)%, respectively. And the proportion of PMN-MDSCs in the control group were (9.6 ± 3.1)%, (4.5 ± 0.6)% and (18.5 ± 0.6)%, respectively. The infected group was significantly higher than the control group 90 and 180 days after infection (t = 3.237, 4.788, P < 0.05, 0.01). 30, 90 and 180 days after infection, the proportion of M-MDSCs in peripheral blood leukocytes of infected mice were (1.8 ± 0.3)%, (1.1 ± 0.1)% and (4.6 ± 1.1)%, respectively. And the proportion of M-MDSCs in the control group were (2.3 ± 0.2)%, (0.5 ± 0.1)% and (3.4 ± 0.9)%, respectively. The infected group was significantly higher than the control group 90 days after infection (t = 3.246, P < 0.05). 180 days after infection, the concentrations of IL-6, IL-13, TNF-α and GM-CSF in the infected mice serum were (315.39 ± 13.58), (339.41 ± 13.35), (223.53 ± 27.49) and (262.31 ± 2.36) pg/ml, respectively, which were significantly higher than that of control group [(14.93 ± 0.55), (50.74 ± 0.88), (50.64 ± 1.64) and (115.28 ± 0.58) pg/ml] (t = 22.100, 21.580, 6.277, 60.460; P < 0.01, 0.01, 0.05, 0.01). Conclusion The proportion of MDSCs in peripheral blood leukocytes increased with time after E. multilocularis protoscoleces infection, mainly of PMN-MDSCs. The concentrations of serum IL-6, IL-13, TNF-α and GM-CSF increased of mice in the late stage of E. multilocularis protoscoleces infection, which may promote the proliferation and activation of MDSCs.

Key words: Echinococcus multilocularis, Protoscoleces, Myeloid-derived suppressor cell, Cytokine