草鱼转化生长因子β1的免疫调节功能及其作用机制

发布时间：2018-05-07 01:22

本文选题：TGF-β1 + 双向免疫调节　；参考：《电子科技大学》2012年博士论文

【摘要】：TGF-β1属于TGF-β超家族，研究表明它在哺乳动物免疫系统中发挥了重要的调节作用，，尤其在外周免疫系统中能诱导激活CD4阳性幼T细胞表达Foxp3，从而分化形成具有维持免疫耐受与抑制自免疫反应功能的调节性T（Treg）细胞亚群。相对于哺乳动物中的深入研究，TGF-β1在包括硬骨鱼的低等脊椎动物免疫系统中的功能地位并不清楚。本论文以草鱼外周血白细胞和头肾白细胞为模型，发现TGF-β1对这两群细胞的活性，T/B细胞标志分子（CD4、CD8α/β和Igμ）和效应分子（TNF-α和IFN-γ）的表达分别产生了刺激和抑制两种调节作用。这种相反的调节功能可能与不同模型中的免疫细胞亚群的种类和状态相关。进一步的研究证明，TGF-β1I型受体activin receptor-like kinase5（ALK5）参与了上述双向调节过程。尤其重要的是ALK5mRNA表达与蛋白水平被TGF-β1明显的下调，进而降低了ALK5阳性细胞在各细胞模型中的比例；这一发现被接下来的TGF-β1免疫中和实验所证实，提示一种基于受体层面的TGF-β1信号通路负调控机制的存在。有趣的是，TGF-β1的双向调节功能和降低受体表达作用均是通过短时的‘触发’方式来实现，而不需要长时间的刺激。这一现象可能与下调ALK5表达的机制来共同防止TGF-β1过度调控。基于哺乳动物免疫系统中Foxp3作为TGF-β1免疫抑制功能重要载体的事实，我们在分离克隆草鱼转录因子Foxp3基因的基础上，发现TGF-β1在硬骨鱼白细胞中不仅明显上调Foxp3基因和蛋白表达水平，而且诱导头肾白细胞分化形成Foxp3阳性细胞亚群。研究证实这类细胞与哺乳动物Treg细胞具有相似的免疫抑制功能，具体表现为对激活白细胞活性的抑制以及下调该细胞中效应分子（TNF-α和IFN-γ）基因的表达。对这种现象的相关机制进一步研究证明草鱼Foxp3阳性细胞亚群是通过分泌TGF-β1与IL-10，以非细胞接触形式来发挥免疫抑制的作用。该结果与哺乳动物诱导性Treg细胞的作用特征相符合。综上所述，本论文首先揭示了TGF-β1在鱼类免疫中的双向调节作用，以及其受体层面的自调控机制，其次阐明了硬骨鱼TGF-β1诱导产生Foxp3阳性细胞亚群的免疫抑制功能及其作用机制。研究结果从分子和细胞层面首次明确了硬骨鱼中“TGF-β1-Foxp3-类Treg细胞”调节机制，为鱼类免疫学增添了新内容。
[Abstract]:TGF- 尾 1 belongs to the TGF- 尾 superfamily and has been shown to play an important regulatory role in the mammalian immune system. Especially in peripheral immune system, activated CD4 positive T cells expressed Foxp3, and then differentiated into regulatory T cell subsets with the function of maintaining immune tolerance and inhibiting autoimmune response. The functional role of TGF- 尾 1 in the lower vertebrate immune system, including bony fish, is not clear compared with that in mammals. In this paper, we found that TGF- 尾 1 stimulated and inhibited the expression of TGF- 尾 1 and the effector molecules TNF- 伪 and IFN- 纬, respectively, on the activity of T / B cell marker molecules, CD4, CD8 伪 / 尾 and Ig 渭, and on the expression of TNF- 伪 and IFN- 纬 in the peripheral blood and head kidney of grass carp. This opposite regulation may be related to the type and state of immune cell subsets in different models. Further studies have demonstrated that TGF- 尾 1 I receptor activin receptor-like kinase5 (ALK5) is involved in the bidirectional regulation. It is particularly important that ALK5mRNA expression and protein levels are significantly down-regulated by TGF- 尾 1, which in turn reduces the proportion of ALK5 positive cells in various cell models, a finding confirmed by subsequent TGF- 尾 1 neutralization experiments. It suggests that there is a negative regulation mechanism of TGF- 尾 1 signaling pathway based on receptor level. It is interesting to note that the bidirectional regulation of TGF- 尾 1 and the reduction of receptor expression are achieved through a short period of 'trigger' without long-term stimulation. This phenomenon may be combined with the mechanism of down-regulation of ALK5 expression to prevent TGF- 尾 1 overregulation. Based on the fact that Foxp3 is an important carrier of TGF- 尾 1 immunosuppressive function in mammalian immune system, we isolated and cloned the Foxp3 gene of grass carp transcription factor. It was found that TGF- 尾 1 not only up-regulated the expression of Foxp3 gene and protein, but also induced the differentiation of head-kidney leukocytes to form Foxp3 positive subsets. It has been demonstrated that these cells have similar immunosuppressive functions to mammalian Treg cells, which can inhibit the activation of leukocytes and down-regulate the expression of effector molecules such as TNF- 伪 and IFN- 纬. Further studies on the mechanism of this phenomenon further demonstrated that Foxp3 positive cell subsets of grass carp play an immunosuppressive role by secreting TGF- 尾 1 and IL-10 in the form of non-cellular contact. The results are consistent with the action characteristics of mammalian induced Treg cells. To sum up, this paper first revealed the bidirectional regulation of TGF- 尾 1 in fish immunity and the self-regulation mechanism of TGF- 尾 1 receptor level, and then clarified the immunosuppressive function and mechanism of TGF- 尾 1 inducing the production of Foxp3 positive cell subsets. The results showed that the regulation mechanism of TGF- 尾 1-Foxp3- like Treg cells in bony fish was first clarified at the molecular and cellular levels, and a new content was added to fish immunology.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2012
【分类号】：R392

【相似文献】