MUCOSAL IMMUNITY IN INFLAMMATORY BOWEL DISEASE

粘膜免疫系统是一个由组织、细胞和 对细菌的防护负有主要责任的介体 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(诱导部位)并进入更大的表面积 其中IgA B细胞和浆细胞，T辅助细胞(Th)和细胞毒T细胞 淋巴细胞(CTL)的产生和分泌性LGA的产生(S-LGA) 抗体产生局部免疫保护(效应点)。一位少校 我们研究的目标是确定Th细胞的性质和 诱导B细胞成为产生LGA的血浆的衍生细胞因子 正常和炎症状态下这些粘膜效应部位的细胞 条件。由于超过80%的粘膜组织存在于 胃肠道，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。溃烂的 结肠炎和克罗恩病的特点是 胃肠道固有层B细胞表达的亚型。这个 我们在两种结肠炎小鼠模型上的实验结果也 表明粘膜免疫系统受到炎症的严重干扰 在大肠里。我们推测，这些的机制 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。最近对小鼠系统的研究表明，CD4+Th 细胞通常可以根据产生的细胞因子的分布进行细分， 现在有令人信服的证据表明人类的Th细胞亚群 自身免疫性、过敏性和传染性疾病。两个子集，Th1和Th2 (L和2型)在小鼠身上表现最好，而L Th细胞 产生白细胞介素2(IL-2)、干扰素-γ(IFN-γ)与肿瘤 细胞免疫(CMI)中的坏死因子-β(TNF-β) 以防止细胞内的寄生虫。2型Th细胞产生IL-4， IL-5、IL-6和IL-10上调IgG1亚类、IgE和IgA抗体 回应。在这项拨款中，我们将检验一种假设，即初始 Th2细胞增加，随后从Th2向Th1型反应转变 发生并引发炎症反应。这一转变从 调节粘膜IgA反应的正常Th2细胞有望 导致异常的粘膜免疫，可能存在于整个胃肠道。至 为了验证这一假设，我们将使用细胞因子基因敲除小鼠以及抗 细胞因子治疗小鼠并确定Th1或Th2通路的变化 影响结肠炎。特别是，我们最近的研究表明， 小鼠口服破伤风类毒素(TT)和粘膜免疫 霍乱佐剂毒素(CT)选择性诱导Th2细胞 血清IgG1和粘膜IgA反应。另一方面，口服免疫 用重组鼠伤寒沙门氏菌表达C片段(Tox C) TT诱导良好的CMI反应和血清IgG2a及较差的粘膜IgA 回应。我们将评估Th2(TT加CT)或Th1(RS)的变化。 小鼠实验性结肠炎的反应模式。 在相关研究中，我们将评估结肠炎是否会导致 全身对口服无反应性(口服耐受性)的崩溃 注射蛋白质抗原。我们将使用口服耐受模型来 白喉类毒素和检测结肠炎是否影响 发展对这种可溶性蛋白疫苗的口服耐受性。我们会 小肠Peyer‘s斑块(PP)与淋巴组织的比较 大肠中的卵泡作为潜在的诱导部位。我们会 确定这两个站点的差异是否导致了该特征 小鼠与大鼠固有层中T细胞和B细胞的反应 肠子。我们还将确定表面免疫球蛋白阳性的B细胞 交通至结肠炎小鼠发炎的粘膜。在最后一系列的 研究中，我们将使用小鼠肠道上皮细胞的体外系统 细胞(IEC)和上皮内淋巴细胞(IEL)，以确定 不适当的细胞和细胞因子相互作用也可能导致肠道 发炎。在这些拟议的研究中，我们将使用两个模型 在小鼠实验性结肠炎中，因为我们对 黏膜免疫系统是从对小鼠的研究中衍生出来的。这些研究 在此续订申请中提出的建议应能为 小鼠IBD期间粘膜免疫系统在胃肠道中的作用。

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.