Dynamic changes of myeloid-derived suppressor cells and regulatory T cells in livers of mice infected with Echinococcus granulosus

Abstract

To investigate the dynamics changes of the myeloid-derived suppressor cells (MDSCs) and regulatory T (Treg) cells in mice infected with Echinococcus granulosus and explore the possible biological significance. Thirty female BALB/c mice of 6 weeks old were randomly divided into the infection and control groups, of 15 mice in each group. Mice in the infection group were intraperitoneally injected with 2 000 E. granulosus protoscoleces, while those in the control group were injected with the same volume of physiological saline. Mouse liver white blood cells were harvested 3 (early stage), 6 (medium stage) and 12 months (late stage) post-infection, and the proportions of MDSCs, their subpopulations (M-MDSCs and PMN-MDSCs) and Treg cells were assessed by flow cytometry. The proportions of MDSCs were (1.61 ± 0.36)%, (5.68 ± 0.69)% and (16.18 ± 0.69)% in mouse liver white blood cells in the infection group 3, 6 and 12 months post-infection with E. granulosus, and (2.19 ± 0.42)%, (0.99 ± 0.07) % and (4.18 ± 0.84)% in the control group, and there were significant differences in the proportion of the MDSCs in mouse liver white blood cells between the infection and control groups 6 and 12 months post-infection (P < 0.01). The proportions of M-MDSCs were (0.69 ± 0.27)%, (5.30 ± 0.72)% and (10.75 ± 0.29)% in mouse liver white blood cells in the infection group 3, 6 and 12 months post-infection, and (0.42 ± 0.24)%, (0.69 ± 0.02)% and (2.12 ± 0.13)% in the control group, and there were significant differences in the proportion of the M-MDSCs in the mouse liver white blood cells between the infection and control groups 6 and 12 months post-infection (P < 0.01). The proportions of PMN-MDSCs were (0.93 ± 0.23)%, (0.32 ± 0.02)% and (5.14 ± 1.03)% in mouse liver white blood cells in the infection group 3, 6 and 12 months post-infection, and (1.77 ± 0.26)%, (0.28 ± 0.05)% and (1.99 ± 0.90)% in the control group, and there were significant differences in the proportion of PMN-MDSCs in mouse liver white blood cells between the infection and control groups 3 and 12 months post-infection (P < 0.05). The proportions of Treg cells were (3.35 ± 0.14)%, (6.24 ± 0.38)% and (3.41 ± 0.07)% in mouse liver white blood cells in the infection group 3, 6 and 12 months post-infection, and (3.48 ± 0.46)%, (3.65 ± 0.45)% and (3.12 ± 0.12)% in the control group, and there were significant differences in the proportion of Treg cells in mouse liver white blood cells between the infection and control groups 6 and 12 months post-infection (P < 0.01). The percentages of both MDSCs and Treg cells increase in mouse liver white blood cells 6 and 12 months post-infection with E. granulosus, and a more remarkable increase is seen in the percentage of MDSCs, which is mainly found in M-MDSCs. These findings suggest that M-MDSCs may play a major immunosuppressive role in the medium and late stages of E. granulosus infection in mice.