The role of IL-4 in the development and function of regulatory Tcells induced by B cells (Treg-of-B cells)

• Main Authors: Szu-Yu Lin, 林思妤
• Other Authors: Bor-Luen Chiang
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/672a8e

碩士 === 國立臺灣大學 === 免疫學研究所 === 105 === Naïve B cells could act as antigen-presenting cells to induce a subpopulation of Foxp3- regulatory T cells, called Treg-of-B cells. Naïve B-cell-primed T cells is through cell-cell contact and independent of IL-10. The suppressive function of Treg-of-B cells partly requires close cell-cell proximity. Therefore, Treg-of-B cells is a population different from natural Treg cells (nTreg) and Type 1 regulatory T cells (Tr1). Recent studies had demonstrated that Treg-of-B cells could be developed as a therapeutic approach against transplant rejection, allergy and rheumatological diseases. However, our studies showed that the differentiation of Treg-of-B cells involved STAT6 phosphorylation and IL-4 secretion. Hence, IL-4 might play a role in induction and/or function of Treg-of-B cells. This study was performed to examine the role of IL-4 signaling pathway in the development and function of Treg-of-B cells. We blocked IL-4 by anti-IL4 antibodies to study the suppressive function and cytokines profile of Treg-of-B cells. However, the result showed no significant difference between experimental group and control group in the suppressive ability, but the levels of IL-4 and IL-10 were lower in neutralized group. We next used Il4-/- mice for further investigation by suppressive function analysis, cytokines profile comparison. the result showed nosignificant difference between WT, Il4-/- Treg-of-B cells in suppressive ability but the level of IL-10 was lower in Il4-/- Treg-of-B(WT) cells. These results might indicate that IL-4 did not affect the induction and function of Treg-of-B cells. Previous study had demonstrated that IL-4 control several immune cell growth and survival. Therefore, we also examined whether IL-4 might maintain the survival of Treg-of-B cells. After induced cell death, we compared the cell death rate experimental group and control group by Annexin V/ PI staining or analyzed apoptosis-related gene expression. The results showed that more cell death induced in IL-4 blocking Treg-of-B cells and Il4-/- Treg-of-B cells. Although IL-2 and IL-4 could rescue the cell death in control group, IL- 2 also partially rescued the cell death of experimental group, but the combination of these two cytokines might enlarged the gap of cell death rate between IL-4 neutralization or not. Furthermore, we analyzed bcl-2 gene family, including anti- apoptotic gene bcl-x, bcl-w and pro-apoptotic gene bax. The results showed that IL-4 blocking Treg-of-B cells expressed slightly lower level of bcl-x. Il4-/- Treg-of-B cells showed more significant difference with lower levels of bcl-x and bcl-w gene expression. The results hinted that IL-4 might involve in maintaining Treg-of-B cells survival. In the deficient of IL-4, more apoptosis might be induced on Treg-of-B cells. In summary, our studies suggested that IL-4 might not affect the induction and function of Treg-of-B cells. In the deficient of IL-4, Treg-of-B cells might tend to go on apoptosis. Therefore, IL-4 might maintain the survival of Treg-of-B cells. In the future, the regulatory mechanism of cytokines production and apoptosis by IL-4-STAT6 signaling pathway might require further researches.