摘要:Galectins 是一種β-galactoside-binding 凝集素,並且擁有某些conserved sequence elements,至今已有多達14種的galectin被發現。它們具有不同的生物功能,如細胞黏著、細胞增生、細胞凋亡及調節發炎反應。其中galectin-9不但是嗜伊紅白血球的趨化因子,促進嗜伊紅白血球產生過氧化物,還可以抑制Th1細胞,在免疫反應中扮演著重要的角色。接觸性過敏反應是一種接觸性皮膚炎的動物模式,主要是經T細胞產生的發炎反應,也可用來評估抗原呈現細胞的功能。其免疫反應主要是由Langerhans細胞及真皮樹突細胞把表皮接觸的hapten帶入淋巴結中並將hapten-major histocompatibility complexes (MHC)呈現給naïve T細胞,造成了致敏化。之後再將同樣的hapten塗抹於皮膚上,使具hapten特異性的T細胞湧入,與hapten在局部反應,釋放細胞激素並吸引更多的發炎細胞至局部,造成了皮膚的腫脹,我們經由測量皮膚的厚度改變來了解發炎反應的嚴重度。在小鼠的接觸性過敏反應中,sGal-9會抑制耳朵的腫脹度,而在sGal-9處理的小鼠中其產生IFN-γ及IL-17的T細胞會減少。然而,在細胞外外加的Gal-9並不代表細胞內Gal-9的功能,因為在Gal-3的研究中就發現了外加Gal-3及細胞內的Gal-3是完全相反的結果,因此我們想藉由Gal-9缺乏的小鼠上探討Gal-9在細胞內的功能。既然Gal-9會抑制Th1細胞,理論上在Gal-9缺乏的小鼠會有較嚴重的接觸性過敏反應。但是令人驚訝的是我們初步的報告顯示Gal-9缺乏的小鼠的接觸性過敏反應比正常鼠來得輕,而其T細胞也比正常鼠的T細胞分泌較少的IFN-γ、IL-17及IL-4。因而我們推測Gal-9缺乏的小鼠其免疫反應較輕微也因此有較輕微的接觸性過敏反應。在此研究中,我們會檢測正常鼠及Gal-9缺乏的小鼠其接觸性過敏反應的嚴重度及皮膚組織中的細胞激素,並將樹突細胞與hapten結合來檢測正常鼠及Gal-9缺乏的小鼠其T細胞的反應,並將此等樹突細胞adoptive transfer至正常鼠及Gal-9缺乏的小鼠以探討in vivo的反應;進一步我們會檢測樹突細胞及T細胞的訊息傳導的差異。此外為了聯結小鼠模式與人類的疾病,我們也將收集接觸性皮膚炎病人的皮膚切片來檢測其Gal-9的含量。經由此研究我們希望可以了解Gal-9在細胞內的功能,並進一步提供其治療疾病的可能性。
Abstract: Galectins (Gals) are members of a β-galactoside-binding animal lectin family and share certain conserved sequence elements. To date, 14 Gals have been cloned in mammals and shown to play modulatory roles in diverse biological processes such as cell adhesion and proliferation, T cell apoptosis, and immunomodulation of inflammation. Gal-9 is most commonly known for its chemotactic activity towards eosinophils as well as induces superoxide production and prolongs cell survival in eosinophils. Besides, Gal-9 has recently been revealed as a negative regulator of Th1 cells, which is important in immune reaction.Contact hypersensitivity (CHS) is an animal model for allergic contact dermatitis. It is a T cell mediated immune response and the well-established method can also evaluate the function of antigen-presenting cells. According to the current paradigm, during the afferent or sensitization phase, hapten-specific T cells are primed by Langerhans cells and/or dermal dendritic cells that migrate from the area of antigen exposure to the skin-draining lymph nodes and present hapten-major histocompatibility complexes (MHC) to naïve T cells. Subsequently, the reapplication of the same hapten to skin results in the influx of hapten-specific T cells that react to the hapten locally, release cytokines, and attract other inflammatory cells. The resultant swelling can be measured and reflects the ongoing immune response.In CHS in mice, the ear swelling response was suppressed by sGal-9. In vitro treatment with sGal-9 resulted in cell apoptosis of CD4, CD8, and hepatic NK cells. sGal-9-treated mice had decreased IFN-γ- and IL-17-producing T cells. However, these extracecullar Gal-9 functions do that stand for the intracellular functions since in Gal-3 studies, the contrasting results had been noted between endogenous and exogenous Gal-3.Therefore, we use the CHS model to define the endogenous Gal-9 function. Since Gal-9 is a negative regulator for Th1 cells, the CHS response should be more severe in Gal-9 -/- mice. Surprisingly, our preliminary data showed that the CHS response in Gal-9 -/- mice is less severe than Gal-9 +/+mice. The T cells secreted less IFN-γ, IL-17 and IL-4 in Gal-9 -/- mice than in Gal-9 +/+ mice. We speculate that the immune response in Gal-9 -/- mice is milder and thus leads to the less severity in CHS response. In this study, we will check the CHS response in Gal-9 +/+ and Gal-9 -/- mice and also the cytokine levels from the lesional skin; the T cell response with hapten-conjugated dendritic cells from Gal-9 +/+ and Gal-9 -/- mice; CHS response by the adoptive transfer of hapten-conjugated dendritic cells from Gal-9 +/+ and Gal-9 -/- mice; the signaling transduction in dendritic cells and T cells from Gal-9 +/+ and Gal-9 -/- mice. To correlate the mice model to human disease, we will collect the human contact dermatitis sample to check the Gal-9 levels. Through this study, we hope that we can find out the intracellular function of Gal-9 and the mechanism elucidated may give us new insight for treating allergic contact dermatitis.