Galectin-3誘發調節性T細胞之研究

Abstract

Galectin-3 是一個分子量為31kDa的蛋白質，屬於哺乳類-半乳糖苷結合蛋白質家族(galectin family)的一員。它表現在細胞核或是細胞質之中，或是以非典型的方式分泌到細胞外；同時它也被認為和自體免疫疾病中產生的發炎反應有所關聯。先前的研究報告中指出部份galectin家族的成員可以藉由影響調節性T細胞的功能進而抑制自體免疫疾病的發生。然而galectin-3在T細胞的調節功能中所扮演的角色還尚未清楚。為了進一步釐清這個問題，我們試圖去了解在試管以及活體的環境之下，galectin-3是否能夠誘發調節性T細胞。我們想要了解galectin-3在誘發調節性T細胞的過程中所扮演的角色，因此在加入galectin-3以後，觀察T細胞在免疫特徵上的變化以及T細胞所表現的轉錄因子。我們同時在動物實驗中研究galectin-3誘發出調節性T細胞以後對於免疫反應及疾病發生的影響。我們利用流式細胞儀分析的結果發現在人類T細胞株(Jurkat cell)或是初級T細胞中，galectin-3可以誘發PD-1以及CTLA-4的表現。除此之外，在加入galectin-3以後也可以使的CD4 T細胞中的轉錄因子FoxP3表現增加；同時也增加了細胞激素TGF-β的產量。這些結果說明了在試管的環境之下，galectin-3的確可以誘發調節性T細胞，並且也使的調節性T細胞中TGF-β的產量上升；然而在加入乳糖以後，這些現象都會因為galectin-3和乳糖結合使得galectin-3被阻擋而無法和表現在T細胞表面的配位基結合而消失。同時在動物實驗中，我們利用腹腔注射galectin-3到小鼠體內以後，分析小鼠的脾臟細胞發現調節性T細胞也會上升。並且在右旋葡聚糖硫酸鈉誘導的小鼠結腸炎中發現galectin-3可以降低小鼠體重下降以及腸道發炎的程度。綜合以上實驗結果，我們發現galectin-3可以誘發調節性T細胞,並且在腸道發炎的小鼠模式中具有保護的效果。因此我們認為galectin-3能夠藉由誘發調節性T細胞來達到治療的效果，在臨床上具有治療及調控免疫反應的潛力。

Galectin-3 is a 31kDa protein, which belong to a family of mammalian b-galactoside-binding proteins. Galectin-3 is present intracellularly within nucleus and cytoplasm or secreted via non-classical pathway outside of cell; and it also has been implicated in the inflammatory immune response in autoimmune diseases. Previous studies demonstrated that several members of galectin family are able to suppress the autoimmune disease via mediating the function of Treg cells. However, the role of galectin-3 mediating the regulatory function in T cells is remained to be further elucidated. In order to address this issue, we attempt to investigate whether galectin-3 induces the Tregs in vitro and in vivo. We examine the immuno phenotype and expression of the transcription factor in T cells after administration of galectin-3. We also investigate the suppressive function of Treg cells induced by galectin-3 in immune response in vivo. Our results demonstrated that galectin-3 induce the expression of PD-1 and CTLA-4 on both Jurkat cells and human primary T cells. In addition, the expression of FoxP3 is up-regulated in CD4 T cells and the frequency of CD4+FoxP3+TGF-β+ T cell is higher in response to galectin-3 according to flow cytometry analysis. These finding indicate that galectin-3 induce the generation of FoxP3+ T cells and increase the production of TGF-β in vitro, while induction of FoxP3+ T cells is abolished by adding lactose to block the interaction between galectin-3 and its ligands on T cells. Furthermore, treatment with recombinant galectin-3 induced the FoxP3+ T cells and ameliorated the severity of DSS-induced Inflammatory Bowel Disease (IBD). In conclusion, our finding demonstrates that galectin-3 induces Tregs and ameliorates the severity of DSS-induced colitis. It suggests that galectin-3 is potential for therapeutic immuno modulation via induction of Tregs.