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Background: Th cells (helper T cells) have multiple functions in Schistosoma japonicum (S. japonicum) infection. Inducible co-stimulator (ICOS) is induced and expressed in activated T lymphocytes, which enhances the development of B cells and antibody production through the ICOS/ICOSL pathway. It remains unclear about the role and possible regulating mechanism of ICOS+ Th cells in the spleen of S. japonicum -infected C57BL/6 mice. Methods: C57BL/6 mice were infected with cercariae of S. japonicum through the abdomen. The expression of ICOS, activation markers, and the cytokine production on CD4+ ICOS+ Th cells were detected by flow cytometry (FCM) and quantitative real-time PCR (qRT-PCR). Moreover, the differentially expressed gene data of ICOS+ and ICOS− Th cells from the spleen of infected mice were obtained by mRNA sequencing. Besides, Western blot and chromatin immunoprecipitation (ChIP) were used to explore the role of Ikzf2 on ICOS expression. Results: After S. japonicum infection, the expression of ICOS molecules gradually increased in splenic lymphocytes, especially in Th cells (P < 0.01). Compared with ICOS− Th cells, more ICOS+ Th cells expressed CD69, CD25, CXCR5, and CD40L (P < 0.05), while less of them expressed CD62L (P < 0.05). Also, ICOS+ Th cells expressed more cytokines, such as IFN-γ, IL-4, IL-10, IL-2, and IL-21 (P < 0.05). RNA sequencing results showed that many transcription factors were increased significantly in ICOS+ Th cells, especially Ikzf2 (P < 0.05). And then, the expression of Ikzf2 was verified to be significantly increased and mainly located in the nuclear of ICOS+ Th cells. Finally, ChIP experiments and dual-luciferase reporter assay confirmed that Ikzf2 could directly bind to the ICOS promoter in Th cells. Conclusion: In this study, ICOS+ Th cells were found to play an important role in S. japonicum infection to induce immune response in the spleen of C57BL/6 mice. Additionally, Ikzf2 was found to be one important transcription factor that could regulate the expression of ICOS in the spleen of S. japonicum -infected C57BL/6 mice. [ABSTRACT FROM AUTHOR]

The morbidity and mortality of malaria are still high. Programmed cell death-1(PD-1) is an important co-inhibitory factor and CD8 T cells with PD-1 were reported to be exhausted cells. It remains unknown what the role of CD4 T cells expressing PD-1 is and what the upstream regulating molecules of PD-1 in CD4 T cells are. The C57BL/6 mice were injected with Plasmodium yoelii ( P. yoelii ) in this study. Expressions of PD-1, activation markers, and cytokines were tested. The differentially expressed genes between PD-1 +/- CD4 T cells were detected by microarray sequencing. Western blot, chromatin immunoprecipitation (ChIP), siRNA, hypoxia inducible factor-1α (HIF-1α) inducer and inhibitor were used to explore PD-1's upstream molecules, respectively. The proportions of PD-1 + CD4 T cells increased post P. yoelii infection. PD-1 + CD4 T cells expressed more activated surface markers and could produce more cytokines. Nuclear factor of activated T cells 1 (NFATc1) was found to be a key transcription factor to induce PD-1 expression after infection. Both the inducer and the inhibitor of HIF-1α could change the expressions of NFATc1 and PD-1 in vivo and in vitro , respectively. Taken together, P. yoelii infection induced NFATc1 expression by HIF-1α. The highly expressed NFATc1 entered the nucleus and initiated PD-1 expression. PD-1 + CD4 T cells appeared to be more activated and could secrete more cytokines to regulate the host's immune responses against malaria., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Wei, Xie, Li, Fang, Liu, Xing, Shi, Mo, Chen, Xie, Yang, Pan, Tang and Huang.)

Background: Th cells (helper T cells) have multiple functions in Schistosoma japonicum ( S. japonicum ) infection. Inducible co-stimulator (ICOS) is induced and expressed in activated T lymphocytes, which enhances the development of B cells and antibody production through the ICOS/ICOSL pathway. It remains unclear about the role and possible regulating mechanism of ICOS + Th cells in the spleen of S. japonicum -infected C57BL/6 mice., Methods: C57BL/6 mice were infected with cercariae of S. japonicum through the abdomen. The expression of ICOS, activation markers, and the cytokine production on CD4 + ICOS + Th cells were detected by flow cytometry (FCM) and quantitative real-time PCR (qRT-PCR). Moreover, the differentially expressed gene data of ICOS + and ICOS - Th cells from the spleen of infected mice were obtained by mRNA sequencing. Besides, Western blot and chromatin immunoprecipitation (ChIP) were used to explore the role of Ikzf2 on ICOS expression., Results: After S. japonicum infection, the expression of ICOS molecules gradually increased in splenic lymphocytes, especially in Th cells ( P < 0.01). Compared with ICOS - Th cells, more ICOS + Th cells expressed CD69, CD25, CXCR5, and CD40L ( P  < 0.05), while less of them expressed CD62L ( P < 0.05). Also, ICOS + Th cells expressed more cytokines, such as IFN-γ, IL-4, IL-10, IL-2, and IL-21 ( P < 0.05). RNA sequencing results showed that many transcription factors were increased significantly in ICOS + Th cells, especially Ikzf2 ( P < 0.05). And then, the expression of Ikzf2 was verified to be significantly increased and mainly located in the nuclear of ICOS + Th cells. Finally, ChIP experiments and dual-luciferase reporter assay confirmed that Ikzf2 could directly bind to the ICOS promoter in Th cells., Conclusion: In this study, ICOS + Th cells were found to play an important role in S. japonicum infection to induce immune response in the spleen of C57BL/6 mice. Additionally, Ikzf2 was found to be one important transcription factor that could regulate the expression of ICOS in the spleen of S. japonicum -infected C57BL/6 mice., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Xie, Wei, Peng, Xie, Li, Fang, Shi, Yang, Huang, Xie, Pan, Tian and Huang.)