TNF Processing in Pulmonary Immunopathology

描述(申请人提供)：感染呼吸道病毒，如流感，特别是高致病性菌株，导致相当大的肺部免疫病理，其中很大一部分是由宿主T细胞反应引起的。这种肺损伤是此类感染临床结局的重要决定因素。我们已经开发了一个模型来区分肺损伤，这种损伤是由于CD8+T细胞识别肺上皮细胞上的病毒抗原及其触发的T细胞效应器活动所致，而不是由病毒本身的细胞病变效应引起的。在这项建议中，我们旨在扩展CD8+T细胞介导的损伤的特征，以剖析与流感肺炎存在的T细胞反应相关的复杂的免疫病理过程。我们发现，在高损伤和微损伤T细胞群体中，将跨膜肿瘤坏死因子处理为其可溶性形式的阈值存在显著差异。作为一个原则证明，我们已经开发出CD8+T细胞，它只表达一种不可切割的跨膜形式的肿瘤坏死因子，并观察到损伤潜力显著降低。由这些T细胞引起的病理改变是显著的间质/间隔细胞浸润，没有明显的肺泡腔浸润，也没有明显的水肿或出血的迹象。此外，尽管WT T细胞介导的损伤的特点是在T细胞结合后12-24小时内PMN瞬时聚集，随后巨噬细胞显著聚集，但在转移突变T细胞后这种PMN流入并不明显。在接受突变T细胞的患者中，气体交换只受到轻微的损害。我们假设，处理跨膜肿瘤坏死因子的阈值决定了CD8+T细胞识别后损伤的严重程度。我们进一步假设，以抗原特异性方式产生的可溶性肿瘤坏死因子介导的损伤增强的机制是肺泡上皮细胞在T细胞识别的反应下诱导中性粒细胞趋化因子的表达，从而导致中性粒细胞早期和短暂地重新聚集到肺泡腔。这似乎是由肿瘤坏死因子-R2(P75)介导的，导致ERK的激活和Egr-1的表达。我们将研究WT和突变的CD8+T细胞群体，以及表达突变的肿瘤坏死因子受体的各种转基因小鼠，以了解CD8+肿瘤坏死因子对可溶性物种的处理如何触发严重的肺损伤，及其调节机制。

DESCRIPTION (provided by applicant): Infection with respiratory viruses such as with influenza, particularly the highly pathogenic strains, results in considerable pulmonary immunopathology, a large component of which results from the host T cell responses. This lung injury is an important determinant of clinical outcome in such infections. We have developed a model to distinguish the lung injury that is specifically due to CD8+ T cell recognition of viral antigen on lung epithelium and T cell effector activities triggered thereby, from that which results from the cyopathic effects of the virus itself. In this proposal we aim to extend the characterization of CD8+ T cell mediated injury to dissect the complex immunopathologic processes associated with T cell responses in the presence of influenza pneumonia. We have found a significant difference between highly injurious and minimally injurious T cell populations in their threshold for processing transmembrane TNF to its soluble form. As a proof of principle, we have developed CD8+ T cells which exclusively express a non-cleavable transmembrane form of TNF, and have observed a marked reduction in injury potential. The pathology triggered by these T cells is remarkable for significant interstitial/septal cellular infiltration without significant infiltration of the alveolar space and without evidence of edema or hemorrhage. Furthermore, while WT T cell-mediated injury is characterized by transient accumulation of PMNs in the first 12-24 hours after T cell engagement, followed by dramatic accumulation of macrophages, this PMN influx was not evident after transfer of the mutant T cells. Gas exchange was only mildly impaired in recipients of the mutant T cells. We hypothesize that the threshold for processing of transmembrane TNF determines the severity of the injury after CD8+ T cell recognition. We further hypothesize that the mechanism of enhanced injury mediated by soluble TNF produced in an antigen-specific fashion is the induction of neutrophil chemoattractant expression by alveolar epithelial cells, in response to T cell recognition, which leads to early and transient neutrophil recruitment to the alveolar space. This appears to mediated by TNF-R2 (p75) leading to exuberant ERK activation and Egr-1 expression. We will study WT and mutant CD8+ T cell populations, and a variety of transgenic mice expressing mutant TNF receptors in order to understand how CD8+ TNF processing to the soluble species triggers severe lung injury, and the mechanisms of regulation.