Abstract:

Objective To investigate the changes of the myeloid-derived suppressor cells (MDSCs) and T helper 17 (Th17) cells in mice infected with Echinococcus granulosus protoscoleces and its implications. Methods Twenty female BALB/c mice of 6 weeks were randomly divided into the infection and normal control groups, each with 10 mice. The mice in the infected group were intraperitoneally injected with 2 000 protoscoleces, and those in the control group were injected with a same volume of normal saline. Spleen cells, peripheral blood leukocytes, and peritoneal cells were collected eight months after infection, in which the percentages of MDSCs, their subpopulations (M-MDSCs and PMN-MDSCs) and Th17 cells were assessed by flow cytometry. The correlations of MDSCs and their subpopulations with Th17 cells were determined by the Pearson correlation analysis.  Results In the infection group, the proportion of MDSCs in spleen cells, peripheral blood leukocytes, and peritoneal cells were（14.72 ± 4.27）%, （57.04 ± 6.78）% and（15.35 ± 5.56）%, respectively, all significantly higher than those in the control group ［(8.84 ± 2.12)%, (30.53 ± 1.58)% and (1.74 ± 0.63)%, respectively］ (P < 0.05). In the infection group, the proportion of M-MDSCs in spleen cells, peripheral blood leukocytes, and peritoneal cells were (1.29 ± 0.24)%, (6.27 ± 2.11)% and(2.14 ± 0.94)%, respectively, all significantly higher than those in the control group[(0.72 ± 0.25)%, (2.11 ± 1.27)%, (0.25 ± 0.06)%](P < 0.05). The proportion of PMN-MDSCs in spleen cells, peripheral blood leukocytes, and peritoneal cells were (9.31 ± 2.65)%, (46.72 ± 5.67)%, (7.06 ± 2.36)% in the infection group, and were (7.07 ± 3.20)%, (25.42 ± 2.05)%, (1.08 ± 0.40)% in the control group, the proportion of PMN-MDSCs in peripheral blood leukocytes and peritoneal cells in infected group were higher than those in control group(P < 0.05). In the infection group, the percentages of Th17 cells in spleen cells, peripheral blood leukocytes, and peritoneal cells were （1.31 ± 0.38）%, （1.85 ± 0.77）% and （2.90 ± 0.24）%, respectively, all significantly higher than those in the control group ［（0.59 ± 0.07）%, （0.35 ± 0.15）% and （0.41 ± 0.12）%, respectively］ (P < 0.05). Pearson correlation analysis showed that there was no correlation between percentages of Th17 and MDSCs in the spleen cells, peripheral blood leukocytes, and peritoneal cells in the infection group (r = -0.354, -0.746, 0.801; P > 0.05), while the monocytic MDSCs percentage was negatively correlated with Th17 cells in spleen in the infection group (r = -0.896, P < 0.05).  Conclusions The percentage of MDSCs and Th17 cells are both increased in mice at late stage of E. granulosus infection, and may play important roles in the development of echinococcosis.

Key words:  Echinococcus granulosus, Protoscoleces, Myeloid-derived suppressor cells, Th17