AUTHOR=Xie Shihao , Wei Haixia , Peng Anping , Xie Anqi , Li Jiajie , Fang Chao , Shi Feihu , Yang Quan , Huang He , Xie Hongyan , Pan Xingfei , Tian Xu , Huang Jun 

TITLE=Ikzf2 Regulates the Development of ICOS+ Th Cells to Mediate Immune Response in the Spleen of S. japonicum-Infected C57BL/6 Mice

JOURNAL=Frontiers in Immunology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.687919

DOI=10.3389/fimmu.2021.687919

ISSN=1664-3224

ABSTRACT=<sec><title>Background</title><p>Th cells (helper T cells) have multiple functions in <italic>Schistosoma japonicum</italic> (<italic>S. japonicum</italic>) 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<sup>+</sup> Th cells in the spleen of <italic>S. japonicum</italic>-infected C57BL/6 mice.</p></sec><sec><title>Methods</title><p>C57BL/6 mice were infected with cercariae of <italic>S. japonicum</italic> through the abdomen. The expression of ICOS, activation markers, and the cytokine production on CD4<sup>+</sup> ICOS<sup>+</sup> Th cells were detected by flow cytometry (FCM) and quantitative real-time PCR (qRT-PCR). Moreover, the differentially expressed gene data of ICOS<sup>+</sup> and ICOS<sup>−</sup> 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.</p></sec><sec><title>Results</title><p>After <italic>S. japonicum</italic> infection, the expression of ICOS molecules gradually increased in splenic lymphocytes, especially in Th cells (<italic>P</italic> &lt; 0.01). Compared with ICOS<sup>−</sup> Th cells, more ICOS<sup>+</sup> Th cells expressed CD69, CD25, CXCR5, and CD40L (<italic>P</italic> &lt; 0.05), while less of them expressed CD62L (<italic>P</italic> &lt; 0.05). Also, ICOS<sup>+</sup> Th cells expressed more cytokines, such as IFN-γ, IL-4, IL-10, IL-2, and IL-21 (<italic>P</italic> &lt; 0.05). RNA sequencing results showed that many transcription factors were increased significantly in ICOS<sup>+</sup> Th cells, especially Ikzf2 (<italic>P</italic> &lt; 0.05). And then, the expression of Ikzf2 was verified to be significantly increased and mainly located in the nuclear of ICOS<sup>+</sup> Th cells. Finally, ChIP experiments and dual-luciferase reporter assay confirmed that Ikzf2 could directly bind to the ICOS promoter in Th cells.</p></sec><sec><title>Conclusion</title><p>In this study, ICOS<sup>+</sup> Th cells were found to play an important role in <italic>S. japonicum</italic> 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 <italic>S. japonicum</italic>-infected C57BL/6 mice.</p></sec>