TNF ALPHA AND CROHNS DISEASE MUCOSAL INFLAMMATION

肿瘤坏死因子- α (tnf - α)被认为是IBD炎症过程的中介。动物研究表明，抗tnf - α治疗后粘膜Th1细胞因子产生下调，这可能是tnf - α产生这种增强粘膜炎症的机制。在一系列患者接受单次抗tnf - α单克隆抗体输注的试验中，tnf - α作为免疫功能和粘膜炎症介质的作用已被证明具有显著的临床反应。对这些患者的随访评估表明，输注的效果延长，反应持续时间长达一年。这种延长的反应在抗tnf - α清除体内很长时间后仍很明显，这表明tnf - α直接破坏性作用的短暂阻断伴随着特征性夸大免疫反应的更持久的正常化。这一概念得到了对抗tnf - α反应患者的平行研究的支持，其中炎症组织中的粘膜Th1细胞因子反应被显示依次下调至未受损伤粘膜的典型水平。这些结果表明，tnf - α可能介导克罗恩病粘膜中ifn - γ的粘膜Th1细胞生成增强。抗tnf - α治疗可能抑制tnf - α介导ifn - γ的产生，导致对大多数克罗恩病患者粘膜炎症的长期影响。为了开始研究tnf - α在调节粘膜Th1功能中的作用，我们开发了一个体外系统，用于克罗恩病样（Th1表型）炎症在固有层单核细胞中，我们已经证明长期暴露于tnf - α上调Th1细胞因子的产生。初步数据表明，这种上调需要非t细胞和非b细胞的存在，并且与IL- 12、IL-18、IL-4和IL-10无关。对外周血细胞进行多次操作以重现这种现象尚未成功，这表明粘膜室的独特特性可能调节tnf - α的作用。为此，含有热溶性因子的LPMC上清液的共培养能够诱导PBMC增加ifn - γ的产生，以响应tnf - α。我们的实验系统将进一步阐明tnf - α调节粘膜Th1细胞功能的机制。此外，它将允许研究确定新的靶点，旨在选择性下调tnf - α介导的治疗方法，增强克罗恩氏黏膜的Th1反应。

Tumor Necrosis Factor-alpha (TNF-alpha) has been implicated as a mediator of inflammatory processes in IBD. A possible mechanism by which TNF-alpha generates this enhanced mucosal inflammation was suggested by studies in animals showing downregulation of mucosal Th1 cytokine production following anti-TNF-alpha treatment. The role of TNF-alpha as a mediator of immune function and mucosal inflammation in Crohn's disease has been demonstrated by dramatic clinical responses in a series of trials in which patients received a single infusion of anti-TNF-alpha monoclonal antibody. Follow-up evaluation of these patients demonstrated prolonged effects of the infusion with duration of response up to one year. This extended response is evident long after anti-TNF-alpha has cleared the body and suggests that the transient block of the direct, damaging effect of TNF-alpha is accompanied by a more sustained normalization of the characteristic exaggerated immune response. This concept is supported by parallel studies of patients responding to anti-TNF- alpha, in which mucosal Th1 cytokine responses in inflamed tissue were shown to be sequentially down-regulated to levels typical of uninvolved mucosa. These results demonstrate that TNF-alpha may mediate the enhanced mucosal Th1 cell production of IFN-gamma seen in Crohn's disease mucosa. It is likely that treatment with anti-TNF-alpha inhibits TNF-alphamediation of IFN-gamma production, resulting in a prolonged effect on mucosal inflammation in the majority of Crohn's patients. To begin to investigate the role of TNF-alpha in modulation of mucosal Th1 function, we have developed an in vitro system for Crohn's disease-like (Th1 phenotype) inflammation in lamina propria mononuclear cells, which we have used to demonstrate that prolonged exposure to TNF-alpha upregulates Th1 cytokine production. Preliminary data suggest that this upregulation requires the presence of non-T-cells and non-B-cells, and is IL- 12, IL-18, IL-4 and IL-10 independent. Multiple manipulations of peripheral blood cells to recreate this phenomenon have not been successful, suggesting that unique properties of the mucosal compartment may regulate the effects of TNF-alpha. To this end, co-culture of LPMC supernatants containing a heat soluble factor is capable of inducing PBMC to increase production of IFN-gamma in response to TNF-alpha. Our experimental system will further elucidate the mechanism(s) of TNF-alpha modulation of mucosal Th1 cell function. Furthermore, it will allow studies to define new targets for therapeutic approaches aimed at selectively downregulating the TNF-alpha mediated, enhancement of Th1 responses in Crohn's mucosa.