Dynamic changes of lymphocyte differentiation and programmed cell death protein ligand 1 expression in mice infected with Schistosoma japonicum

Abstract

Abstract:

Objective To evaluate the effect of Schistosoma japonicum infection on the lymphocyte differentiation and the programmed cell death protein ligand 1 （PD-L1） expression in infected mice. Methods Thirty BALB/c mice were randomly divided into infected group and uninfected groups. Mice in infected group were each infected with 20 ± 2 cercariae through abdominal skin. Three mice from each group were euthanized before infection and 2, 4, 6, 8, 10 weeks after infection and the lymphocytes were isolated from livers and spleens. The dynamic changes of the lymphocyte proportions for CD3⁺ T cells (CD3⁺CD19^-), CD19⁺ B cells (CD3^-CD19⁺), CD4⁺ T cells (CD3⁺CD19^-CD4⁺CD8^-) and CD8⁺ T cells(CD3⁺CD19^-CD4^-CD8⁺) and PD-L1 expression on these subset cells were detected by flow cytometry. The differences between groups were statistically analyzed by ANOVA test. Results Both in liver and spleen, the lymphocyte populations of CD3⁺ T cells, CD19⁺ B cells and CD4⁺ T subsets, decreased significantly in mice infected with S. japonicum for 4-8 weeks compared to the populations before infection (P < 0.05, 0.01 or P > 0.05). However, in livers of mice infected with S. japonicum, the population of CD8⁺ T cell subset at 6 week [(38.03 ± 7.41)%] after infection was significantly higher than uninfected group [(23.37 ± 3.98)%]（P < 0.01）, but no significant change in spleen. More interestingly, the expression of PD-L1 on CD19⁺ B cells at 6 week [(7.25 ± 3.47)%] after infection with S. japonicum was significantly inhibited compared with the uninfected group [(22.77 ± 8.90)%] (P < 0.01) while the changes in spleen was later than that in liver, at 8 week[(22.37±4.01)%] after infection was significantly inhibited compared with the uninfected group[(51.97 ± 1.62)%] (P < 0.01) and remained at low level thereafter, in both liver and spleen. The expression of PD-L1 on CD3⁺ T and CD4⁺ T cells in liver during 2 to 10 weeks (P < 0.05, 0.01 or P > 0.05) and in spleen during 4 to 8 weeks after infection was lower than that of the uninfected group (P <0.05). The expression of PD-L1 on CD8⁺ T cells in both liver and spleen was not changed at the early infection stage, but increased significantly at 10 weeks [(34.80 ± 3.68)%, (31.90 ± 2.53)%] after infection compared to the level before infection [(25.5 ± 0.80)%, (29.91 ± 3.55)%] (P < 0.01). Conclusion The lymphocyte proportion of CD19⁺ B, CD3⁺ T and CD4⁺ T cells were induced to decrease significantly in livers and spleens of mice infected with S. japonicum, however, the change in CD8⁺ T cell proportion was not significant in comparison to the level before infection. Similar trend was observed in PD-L1 expression on these lymphocyte subsets with significant decrease on CD19⁺ B, CD3⁺ T and CD4⁺ T lymphocytes, but significant increase on CD8⁺ T cells at later infection stage. These changes of lymphocytes in liver occur earlier than that in spleen.

Key words: Schistosoma japonicum, BALB/c mice, Lymphocyte, Flow cytometry, PD-L1

CLC Number:

R383.24

Xiao-ling WANG, Yuan HU, Yu-xin XU, Hua LIU, Jian-ping CAO. Dynamic changes of lymphocyte differentiation and programmed cell death protein ligand 1 expression in mice infected with Schistosoma japonicum[J]. CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES, 2018, 36(6): 579-585.

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