An Animal Model of Hemophagocytic Lymphohistiocytosis

描述（由申请人提供）：噬血细胞性淋巴组织细胞增生症（HLH）是一种过度和异常免疫激活的儿童疾病，其特征是骨髓严重受损，死亡率接近50%。几乎所有的HLH患者都严重缺乏T细胞和NK细胞的细胞毒性杀伤，并且已经发现这些患者中的许多人在编码穿孔素的基因中存在突变。我们开发了一种新的这种疾病的小鼠模型，其中穿孔素缺陷（prf）小鼠的挑战与淋巴细胞性脉络丛脑膜炎病毒（LCMV）。感染后，prf小鼠形成与HLH几乎相同的表型。使用该模型，我们已经发现HLH表型直接由CD 8 + T细胞的干扰素γ（IFN-g）的异常过量产生驱动。此外，我们发现来自prf小鼠的DC具有增加量的病毒抗原，并且在感染后获得增加的刺激病毒特异性T细胞的能力。这些发现暗示DC群体增加的抗原呈递是prf小鼠中IFN-g过度产生的根本原因，并表明穿孔素通常起下调抗原呈递的作用。已知表达穿孔素的多种细胞类型与DC相互作用。为了鉴定这些群体中的哪一个将正常下调DC的刺激，我们进行了一系列细胞去除、转移和骨髓移植实验。这些研究表明，表达穿孔素的细胞类型可以影响DC功能和体内IFN-γ的产生，并表明CD 8 + T细胞是发挥这种调节作用的最关键的细胞类型。基于我们的初步研究，我们假设CD 8 + T细胞对所选树突状细胞的穿孔素依赖性细胞毒性杀伤限制了抗原在DC群体中的进入和/或持久性，从而限制了免疫激活。为了验证我们的假设，我们将追求以下具体目标：目标1。定义LCMV感染后WT和prf DC亚群之间抗原处理和呈递的差异。目标2）确定CD 8 + T细胞是否是通过穿孔素依赖性机制抑制DC刺激功能的主要细胞类型。该项目将导致更好地了解细胞毒性功能如何调节免疫反应，并导致改善HLH患者的治疗方法，也许还有许多其他免疫病理学疾病。

DESCRIPTION (provided by applicant): Hemophagocytic lymphohistiocytosis (HLH) is a childhood disorder of excessive and abnormal immune activation, characterized by severe damage to the bone marrow, and a mortality rate approaching 50%. Nearly all patients with HLH have a severe deficiency of cytotoxic killing by T and NK cells, and many of these patients have been found to harbor mutations in the gene encoding perforin. We developed a novel murine model of this disorder, in which perforin deficient (prf) mice are challenged with lymphocytic choriomeningitis virus (LCMV). Following infection, prf mice develop a phenotype that is nearly identical to HLH. Using this model, we have discovered that the HLH phenotype is directly driven by the abnormal overproduction of interferon gamma (IFN-g) by CD8+ T cells. Additionally, we have found that DC's from prf mice harbor increased amounts of viral antigen and acquire increased capacity to stimulate virus-specific T cells after infection. These findings implicate increased antigen presentation by DC populations as the underlying cause of IFN-g overproduction in prf mice, and suggest that perforin normally functions to down modulate antigen presentation. Multiple cell types that express perforin are known to interact with DC's. In order to identify which of these populations would normally down modulate stimulation by DC's, we have performed a series of cell depletion, transfer, and bone marrow transplantation experiments. These studies have revealed that perforin-expressing cell types can influence both DC function and in vivo IFN-g production, and suggest that CD8+ T cells are the most critical cell type exerting this regulatory effect. Based on our preliminary studies, we hypothesize that perforin-dependant cytotoxic killing of selected dendritic cells by CD8+ T cells limits the entry and/or persistence of antigen in DC populations, and thereby limits immune activation. To test our hypothesis, we will pursue the following specific aims: Aim 1.) Define how antigen handling and presentation differ between WT and prf DC subsets after LCMV infection. Aim 2.) Determine whether CD8+ T cells are the principle cell type that suppresses DC stimulatory function via a perforin-dependant mechanism. This project will lead to better understanding of how cytotoxic function regulates the immune response and lead to improved therapies for patients with HLH and perhaps many other immunopathologic disorders.