【作者】 黄琼；

【导师】 郑志忠；

【作者基本信息】 复旦大学 ， 皮肤病与性病学， 2004， 博士

【摘要】 银屑病是一种以角质形成细胞异常增生伴角化不全，真皮乳头微血管增生及炎症细胞浸润为主的慢性皮肤病。我国约有300万以上患者，而全世界则有近2000万患者，多为青壮年，严重影响了人们的心理健康和社会经济建设。银屑病的发病机理目前尚不清楚，受到遗传代谢异常及神经心理等诸多因素的影响，免疫功能的异常在其发病中起到重要的作用，现在大多认为其是Th1反应为主的免疫性疾病。 朗格汉斯细胞(LC)是一种位于表皮的特殊的树突状细胞(DC)，其在银屑病发病机制中的作用逐渐受到重视。人DC和单核细胞可产生IL-12和IL-18，诱导T细胞(包括CD4+和CD8+)和NK细胞产生IFN-γ，IFN-γ又反过来可以诱导DC和单核细胞产生IL-18BP，其与IL-18结合抑制IFN-γ的产生，因此形成IL-18／IL-18BP负反馈环路调节Th1反应。我们既往的研究发现银屑病血清中存在细胞因子异常，本文的研究发现银屑病患者血浆中IL-18BPa的浓度比正常人减少，进行期血浆中的浓度最低，退行期血浆中的浓度与正常人相近，与银屑病PASI评分呈负相关性，说明在银屑病外周血中存在抑制因子IL-18BPa的下降，IL-18／IL-18BP负反馈环路的异常，使Th1反应增强，可能在银屑病的发病机制中起到重要作用。 LC在体外可由外周血单核细胞培养获得，目前认为外周血单核细胞是LC的前体细胞。IFN-γ主要由外周血单个核细胞(PBMC)中的T淋巴细胞和NK细胞产生，而单核细胞是产生IL-18BP的主要细胞。人类IL-18BP基因至少有四种不同的亚型IL-18BPa、IL-18BPb、IL-18BPc和IL-18BPd。其中IL-18BPa和IL-18BPc与IL-18具有高亲和力，结合后抑制IL-18的生物功能，而IL-18BPb和IL-18BPd不能中和IL-18的生物功能。外周血单核细胞可以表达IL-18BPa和IL-18BPb。我们发现IL-18BPa在银屑病血浆中浓度比正常人减少，是否是由于单核细胞本身合成功能异常引起，本文对此进行了进一步的研究。结果发现银屑病患者和正常人外周血PBMC在IL-12的刺激下均表达IFN-γmRNA和IL-18BPa mRNA，而没有IL-18BPb mRNA的表达，TGF-β1可以通过下调IFN-γ mRNA而降低IL-18BPa mRNA表达，且银屑病中IFN-γ mRNA和IL-18BPa mRNA的表达均显著高于正常人对照，进一步证实银屑病以Th1反应为主，且存在IL-18／IL-18BP负反馈环路，IL-18BPa mRNA的表达受到IFN-γ的调控。银屑病患者外周血细胞流式细胞分析发现银屑病患者NK细胞计数显著高于正常人对照，可能与IFN-γ mRNA的表达的显著增强相关。因此在IL-12的刺激下，银屑病单核细胞产生银屑病单核细胞及其来源的朗格汉斯细胞IL18BP的表达.勺.工L一18BPa mRNA表达的增加可能是由于工FN一Y mRNA的表达上调。银屑病患者外周血单个核细胞(PBMC)在工L一12的刺激24小时后培养液上清中工L一18BPa蛋白浓度与正常人比较无统计学差异，可能是蛋白尚未充分合成的缘故，因此银屑病单核细胞不存在合成工L一18BPa mRNA的功能异常。 我们的研究发现单核细胞本身可能不存在合成工L--18BPa功能异常，那么单核细胞来源的LC是否存在合成工L一 18BPa的功能异常，从而在银屑病皮损的发生中起到重要作用呢?我们对此进行了研究发现，银屑病患者单核细胞来源LC在形态和表形上与正常对照没有明显差异，工FN一Y不但可以诱导LC表面HLA一DA的表达上调，而且可以诱导LC分泌IL一18BPa mRNA和IL一18BPa蛋白的表达，但与正常人对照没有显著差异，说明银屑病中单核细胞来源的朗格汉斯细胞合成工L一18BPa的功能与正常人对照相近。 银屑病病中单核细胞及其来源LC与正常对照在合成IL一18BPa mRNA功能上无差异，而外周血中IL一18BPa蛋白浓度降低，可能是复杂网络系统相互作用的结果，从而导致IL一18/IL一18BP负反馈环路的异常，Thl反应增强，银屑病加重和发生。更多还原

【Abstract】 Psoriasis is an inflammatory disease with resultant hyperplasia and abnormal differentiation of epidermal keratinocytes, dilatation of capillary vessels in papillae of corium and infiltration and recruitment of inflammatory cells.There are more than 3 million patients with psoriasis in China while about 20 millions in the world. Usually patients are in the middle of the age and psoriasis has severe adverse impacts upon both patients’ psychological health and social economic construction. So far the pathogenesis of psoriasis is not well understood, but it is considered to be associated with many factors such as abnormity of heredity, metabolism and neuropsychology. The disturbance of immune function plays a more important role in this disease. Today psoriasis has been generally regarded as a T-helper (Th) 1-dominated disease.Langerhans cells (LCs) are a kind of immature dendritic cells (DCs), residing in the superbasal layer of the epidermis. Their role in the pathogenesis of psoriasis has been gradually recognized. Human DCs and monocytes can secrete IL-12 and IL-18, which induce T cells including CD4+ and CD8+ and NK cells to produce IFN- Y . IFN- y reversely induces DCs and monocytes to secrete IL-18BP, then IL-18BP binds with IL-18 and depress the secretion of IFN- γ .So there forms the IL-18/IL-18BP negative feedback loop to regulate Thl cellular immune responses. Our previous study indicated there were abnormal levels of cytokines in the serum of psoriatic patients. In this study we found the level of IL-18BPa in the plasma of psoriatic patients is significantly lower than that of normal controls. The lowest level appears in the progression phase, but that in the regression phase is similar to normal controls. It is also found that the level of IL-18BPa has a negative correlation with PASI score. This finding indicates that IL-18BPa as an inhibitor decreases in the plasma of psoriatic patients. The abnormal IL-18/IL-18BP negative feedback loop will enhance Thl cellular immune responses, and this may play an important role in the pathogenesis of psoriasis.In vitro LCs can be obtained from the peripheral blood monocytes. At present monocytes are considered to be the precursors of LCs. IFN- y is secreted mainly by T cells and NK cells, while IL-18BP is produced chiefly by monocytes. In human, there exist at least four isoforms of IL-18BP. IL-18BPa and IL-18BPc have high affinity to neutralize IL-18, and then suppressing IFN-γ production. But IL-18BPband IL-18BPd, on the other hand, don’t have such function. IL-18BPa and IL-18BPb can be both expressed in the peripheral blood monocytes. It is found that the plasma level of IL-18BPa in patients with psoriasis is lower than that in normal controls. In our study we investigated whether that is due to the abnormal synthess function of IL-18BP by monocytes in psoriatic patients. We found IL-12 induced peripheral blood mononuclear cells to express IFN-y mRNA and IL-18BPa mRNA both in psoriatic patients and normal controls, but there was no expression of IL-18BPb mRNA. TGF- {3 1 can suppress the expression of IL-18BPa mRNA by downregulating IFN-Y mRNA, and the expression of IFN-Y mRNA and IL-18BPa mRNA are significantly higher in psoriatic patients than in normal controls. This result proved further that there is Thl cellular immune responses in the psoriasis, that the IL-18/IL-18BP negative feedback loop exits and IL-18BPa mRNA expression was regulated by IFN- Y .The count of NIC cells by flow cytometer in psoriatic patients is siginificantly higher than in normal controls, probally associated with the increase of IFN- Y mRNA expression. Therefore, under the stimulation of IL-12, the high expression of IL-18BPa mRNA by monocytes of psoriatic patients is probally due to the upregulation of IFN- Y mRNA. After 24 hours stimulation of IL-12, the level of IL-18BPa in the supernatant of psoriatic peripheral blood mononuclear cells exhibits no significant difference from normal controls. The reason might be that the protein hasn’t been produced sufficiently in 24 hours.更多还原