TNF ALPHA AND CROHNS DISEASE MUCOSAL INFLAMMATION

肿瘤坏死因子-α（TNF-α）已被认为是IBD中炎症过程的介质。 动物研究表明，抗TNF-α治疗后粘膜Th 1细胞因子产生下调，提示TNF-α产生这种增强的粘膜炎症的可能机制。 TNF-α作为免疫功能和粘膜炎症介质在克罗恩病中的作用已通过一系列试验中的显著临床反应得到证实，在这些试验中，患者接受抗TNF-α单克隆抗体的单次输注。 对这些患者的随访评价表明，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清除身体后很长时间内是明显的，并表明TNF-α的直接破坏作用的短暂阻断伴随着特征性过度免疫反应的更持续的正常化。 这一概念得到了对抗TNF-α应答患者的平行研究的支持，其中炎症组织中的粘膜Th 1细胞因子应答显示出顺序下调至未受累粘膜的典型水平。 这些结果表明，TNF-α可能介导克罗恩病粘膜中观察到的增强的粘膜Th 1细胞产生IFN-γ。 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Th 1功能中的作用，我们已经开发了一种用于固有层单核细胞中克罗恩病样（Th 1表型）炎症的体外系统，我们已经使用该系统来证明长期暴露于TNF-α上调Th 1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，并且不依赖于IL- 12、IL-18、IL-4和IL-10。 多次操作外周血细胞来重现这种现象尚未成功，这表明粘膜隔室的独特性质可能调节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响应于TNF-α而增加IFN-γ的产生。 我们的实验系统将进一步阐明TNF-α调节粘膜Th 1细胞功能的机制。 此外，它将允许研究确定新的治疗方法的目标，旨在选择性下调TNF-α介导的，增强克罗恩病粘膜中的Th 1应答。

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.