MUCOSAL IMMUNITY IN INFLAMMATORY BOWEL DISEASE

粘膜免疫系统是由组织、细胞和免疫球蛋白组成的庞大网络。 介体，其承担保护免受细菌感染的主要责任， 以及通常通过粘膜获得的病毒感染。 这种外部分泌物的免疫系统可以分为几个部位， 遇到抗原（诱导位点）并进入更大的表面积 其中伊加B细胞和浆细胞、T辅助（Th）细胞和细胞毒性T 淋巴细胞（CTL）发生，分泌型IgA（S-IgA）的产生 抗体导致局部免疫保护（效应位点）。一个主要 我们研究的目标是表征Th细胞的性质， 用于诱导B细胞成为产生IgA的血浆的衍生细胞因子 在正常和炎症条件下， 条件由于超过80%的粘膜组织被发现在胃肠道中， 胃肠道（GI），我们对粘膜免疫的大部分知识 源于对肠道免疫反应的研究。溃疡性 结肠炎和克罗恩病的特征在于 由胃肠道固有层中的B细胞表达的同种型。的 我们对两种结肠炎小鼠模型的实验结果也 表明粘膜免疫系统受到炎症的极大干扰， 在大肠中。我们假设，这些机制 炎症结肠粘膜中B细胞反应的改变是由于 CD 4 + Th细胞亚群和细胞因子谱的变化， 这些子集。最近在小鼠系统中的研究表明，CD 4 + Th 细胞通常可以基于产生的细胞因子的分布而细分， 现在有令人信服的证据表明， 自身免疫性、过敏性和感染性疾病。两个子集，Thl和Th 2 (type 1型和2型）在小鼠和1型Th细胞中的特征最好 产生白细胞介素-2（IL-2）、干扰素γ（IFN-γ）和肿瘤 坏死因子-β（TNF-β）用于细胞介导的免疫（CMI）， 来抵御细胞内的寄生虫2型Th细胞产生IL-4， IL-5、IL-6和IL-10并上调IgG 1亚类、IgE和伊加抗体 应答在这篇论文中，我们将研究一个假设， Th 2细胞增加，随后从Th 2型反应转变为Th 1型反应 发生并引发炎症反应。这种从 预期调节粘膜伊加应答的正常Th 2细胞 导致异常的粘膜免疫，可能在整个胃肠道。到 我们将使用细胞因子敲除小鼠以及抗- 细胞因子处理的小鼠，并确定Th 1或Th 2途径的改变 影响结肠炎症。特别是，我们最近的研究表明， 用破伤风类毒素（TT）口服免疫小鼠， 佐剂霍乱毒素（CT）选择性诱导Th 2细胞，其调节 血清IgG 1和粘膜伊加应答。另一方面，口服免疫 用表达C片段的重组鼠伤寒沙门氏菌（Tox C） TT诱导良好的CMI反应和血清IgG 2a和粘膜伊加 应答我们将评估Th 2（TT加CT）或Thl（rS. 鼠伤寒-毒素C）的反应模式与实验性结肠炎的小鼠。 在相关的研究中，我们将评估结肠炎症是否会导致 口服耐受性（oral tolerance） 施用蛋白质抗原。我们将使用口服耐受模型， 白喉类毒素和测试是否结肠炎症影响 发展对这种可溶性蛋白疫苗的口服耐受性。我们将 比较小肠Peyer集合淋巴结（PP）与淋巴结 大肠中的滤泡作为潜在的诱导位点。我们将 确定这两个位点的差异是否导致了 小细胞与大细胞固有层中的T和B细胞反应 肠子我们还将确定表面IgG阳性B细胞是否 运输到结肠炎小鼠的发炎粘膜。在最后一系列的 研究中，我们将使用小鼠肠上皮细胞的体外系统， 细胞（IEC）和上皮内淋巴细胞（IEL），以确定是否 不适当细胞和细胞因子的相互作用也可导致肠 炎症在这些拟议的研究中，我们将使用两种模型， 实验性结肠炎的小鼠，因为我们的理解， 粘膜免疫系统已经从小鼠的研究中得到。研究 在这次更新申请中提出的建议应该产生新的见解 粘膜免疫系统在小鼠IBD期间胃肠道中的作用。

The mucosal immune system is a vast network of tissues, cells and mediators which bears a major responsibility for protection from bacterial and viral infections which are normally acquired through mucous membranes. This immune system of external secretions can be divided into sites where antigen is encountered (inductive sites) and into larger surface areas where IgA B cells and plasma cells, T helper (Th) cells and cytotoxic T lymphocytes (CTLs) occur, and where production of secretory lgA (S-lgA) antibodies result in local immune protection (effector sites). A major goal of our research has been to characterize the nature of Th cells and derived cytokines for induction of B cells to become lgA-producing plasma cells in these mucosal effector sites under both normal and inflamed conditions. Since over 80 % of mucosal tissues are found in the gastrointestinal (GI) tract, most of our knowledge about mucosal immunity has stemmed from studies of immune responses in the gut. Ulcerative colitis and Crohn's disease are characterized by alterations in the isotypes expressed by B cells in the lamina propria of the GI tract. The results of our experiments with two mouse models of colitis have also shown that the mucosal immune system is greatly perturbed by inflammation in the large intestine. We postulate that the mechanism of these alterations of B cell responses in inflamed colonic mucosa are due to changes in CD4+ Th cell subsets and in the cytokine profiles exhibited by these subsets. Recent studies in the murine system have shown that CD4+ Th cells can often be subdivided based upon profiles of cytokines produced, and convincing evidence is now at hand for Th cell subsets in humans with autoimmune, allergic and infectious diseases. Two subsets, Thl and Th2 (type l and type 2) are best characterized in mice and type l Th cells produce interleukin-2 (IL-2), interferon gamma (IFN-gamma) and tumor necrosis factor-beta (TNF-beta) for cell-mediated immunity (CMI) in order to protect against intracellular parasites. Type 2 Th cells produce IL-4, IL-5, IL-6 and IL-10 and upregulate IgG1 subclass, IgE and IgA antibody responses. In this grant, we will examine the hypothesis that an initial increase in Th2 cells followed by a shift from Th2 to Thl type responses takes place and initiates an inflammatory response. This shift away from normal Th2 cells which regulate mucosal IgA responses would be expected to result in aberrant mucosal immunity, perhaps in the entire GI tract. To test this hypothesis we will use cytokine knockout mice as well as anti- cytokine treated mice and determine how alterations in Thl or Th2 pathways affect colonic inflammation. In particular, our recent studies have shown that oral immunization of mice with tetanus toxoid (TT) and the mucosal adjuvant cholera toxin (CT) selectively induces Th2 cells which regulate serum IgG1 and mucosal IgA responses. On the other hand, oral immunization with recombinant Salmonella typhimurium expressing the C fragment (Tox C) of TT induced good CMI responses and serum IgG2a and poor mucosal IgA responses. We will assess changes in the Th2 (TT plus CT) or Thl (rS. typhimurium -Tox C) response patterns in mice with experimental colitis. In related studies, we will assess whether colonic inflammation causes a breakdown in systemic unresponsiveness (oral tolerance) to orally administered protein antigens. We will use the model of oral tolerance to diphtheria toxoid and test whether colonic inflammation affects the development of oral tolerance to this soluble protein vaccine. We will compare Peyer's patches (PP) in the small intestine with lymphoid follicles in the large bowel as potential inductive sites. We will determine if differences in these two sites account for the characteristic T and B cell responses in the lamina propria of the small versus large intestine. We will also determine whether surface IgG-positive B cells traffic to the inflamed mucosa of colitic mice. In a final series of studies, we will use in vitro systems of murine intestinal epithelial cells (IEC) and intraepithelial lymphocytes (IEL), to determine if inappropriate cell and cytokine interactions could also lead to intestinal inflammation. In these proposed studies, we will use two models of experimental colitis in the mouse, since much of our understanding of the mucosal immune system has been derived from studies in mice. The studies proposed in this renewal application should yield new insights into the role of the mucosal immune system in the GI tract during murine IBD.