2013 Fiscal Year Annual Research Report
異なるヘルパーT細胞による腸管IgAの変化と腸内細菌叢への影響の検討
| Project/Area Number |
13F03216
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
ファガラサン シドニア 独立行政法人理化学研究所, 統合生命医科学研究センター, チームリーダー
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| Co-Investigator(Kenkyū-buntansha) |
TAKAHASHI Lucia 独立行政法人理化学研究所, 統合生命医科学研究センター, 外国人特別研究員
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| Keywords | IgA / Foxp3 / gut bacteria / Peyer's patches / germinal center |
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| Research Abstract |
To elucidate the roles of T_<FE> cells differentiated from distinct T cell subsets in the expansion and selection of immunoglobulin A (IgA)-producing B cells, we performed adoptive transfer of Foxp3^+ T cells alone or together with naïve T cells into mice that lack T cells (CD3^<-/-> mice). Also, to test whether the action of Foxp3^+ T cells inside the germinal centers (GCs) is important for regulating gut homeostasis, we performed the co-transfer experiment using Foxp3^+ T cells isolated from Bc16^<yfp/yfp> mice (herein Foxp3^<Bcl6-> T cells), which are incapable to enter the GCs.
1. Analysis of gut tissues
We found that mice transferred with naïve T cells alone develop intestinal inflammation, especially in the large intestine. We could observe uncontrolled T cell expansion, together with a reduction in the number of IgA^+ B cells in the GCs of Peyer's patches (PPs) and in the number of IgA^+ plasma cells in the lamina propria of the small intestine (SILP). The co-transfer of Foxp3^+ T cells could rescue inflammation and IgA production to the same leval as wild type control animals. Interestingly, the co-transfer of Foxp3^<Bcl6-> T cells could prevent inflammation but failed to rescue the number of IgA+ plasma cells, indicating that the touchdown of Foxp3^+ T cells inside the GCs is important to induce proper IgA responses.
2. Analysis of IgA sequence
To check the nature of IgAs induced with or without Foxp3^+ T cell control inside the GCs, IgA^+ plasma cells from SILP of transferred mice were single cell sorted and the V region of the Ig heavy gene was sequenced. We found that IgA from mice transferred with Naïve T cells or Naïve T plus Foxp3^<Bcl6->T cells have lower mutation index, suggesting less effective antibody selection in PPs when Foxp3^+ T cells are absent from GCs.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
It is known that Foxp3^+ T cells can regulate gut homeostasis by preventing inflammation but unexpectedly, we found that if Foxp3^+ T cells are unable to enter the GCs, they fail to rescue the number of IgA^+ plasma cells, as well the quality of IgAs, indicating that the regulation of Foxp3^+ T cells inside the germinal centers are essential for appropriate IgA selection.
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| Strategy for Future Research Activity |
In the next year, I wish to analyze how T cells and gut IgA modulate the gut bacterial communities. To do so, we will perform 16S ribosomal RNA (rRNA) gene pyrosequencing of cecal contents from T cell-transferred mice to examine how bacterial composition changes depending on the presence of Foxp3^+ T cells and IgA quality. Also, we will analyze how IgAs with different qualities bind to fecal bacteria using flow cytometry.
Moreover, to examine how bacterial communities modulate the gut immune system, we will transfer bacteria from T cell-transferred mice to germ-free mice and analyze the host response to the different bacterial communities (flow cytometry, histology, sequencing of IgA).
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