Lymphotoxin and Lymphoid Neogenesis

描述(由申请人提供)：本项目的目标是了解淋巴器官的发育和在个体发育和炎症中的作用。定向过表达淋巴毒素(LT)(LTA或LTab)可导致具有淋巴器官特征的异位淋巴集合体。这些“第三淋巴器官”(TLO)也见于自身免疫中的许多慢性炎症情况，包括胰岛素依赖型糖尿病(IDDM)的早期阶段。高内皮微静脉(HEV)基因在发育、TLO和急性炎症中受到调控。在正常和HEC6ST-LacZ小鼠中，以表达Pnad、LTbR和HEV亚转移酶(HEC-6st)为特征的成熟HEV表型依赖于通过LTbR的信号。免疫后，戊型肝炎病毒瞬间恢复到未成熟的表型，然后恢复。恢复依赖于B细胞和LTbR。淋巴管生成也发生在TLO和急性炎症中。在免疫后的早期，LV和HEV标志物均阳性的血管的出现取决于LTbR。一种新型的双峰树状大分子通过磁共振成像(MRI)和荧光显示淋巴管，结果表明LT缺乏的小鼠有LV缺陷。目前尚不清楚LT如何促进淋巴管生成。我们将检验两个假设。假设一、淋巴管在炎症和发育过程中由LT调节；假设二、通过LT的持续信号对于淋巴器官的维持和功能是必要的，特别是对于HEV和LV。其具体目的是：1.通过确定B细胞是否产生调节HEV和LV的LT配体，通过评估巨噬细胞在淋巴管生成中的作用，以及通过确定双阳性血管是否代表HEV出芽的LV，来确定HEV和LV在急性炎症中是如何调节的；2.通过评估血管的表型、密度和功能、巨噬细胞的作用以及LTbR和TNFR信号，确定HEV和LV在慢性炎症中是如何调节的；3.通过评估LV功能和表型来确定LT是否以及如何影响构成LV。通过LTbR和TNFR抑制剂的治疗以及通过四环素诱导系统打开和关闭LT来确定是否需要持续的LT信号来维持TLO中的HEV和LV。阐明HEV和LV的调节将提供抑制其自身免疫的策略，并允许控制胰岛素炎。

DESCRIPTION (provided by applicant): The goal of this project is to understand lymphoid organ development and function in ontogeny and inflammation. Directed over expression of lymphotoxin (LT) (either LTa or LTab) results in ectopic lymphoid aggregates with the characteristics of lymphoid organs. These "tertiary lymphoid organs" (TLOs) are also seen in many situations of chronic inflammation in autoimmunity, including the early stages of insulin dependent diabetes mellitus (IDDM). High endothelial venule (HEV) genes are regulated in development, in TLOs, and in acute inflammation. The mature HEV phenotype, characterized by expression of PNAd, LTbR, and a HEV suIfotransferase (HEC-6ST) depends on signaling through the LTbR in normal and HEC6ST- lacZ mice. After immunization, HEVs revert transiently to an immature phenotype and then recover. The recovery is dependent on B cells and LTbR. Lymphangiogenesis also occurs in TLOs and in acute inflammation. At early times after immunization, the occurrence of vessels that are positive for both LV and HEV markers is dependent on LTbR. Results with a novel bimodal dendrimer that visualizes lymphatic vessels by magnetic resonance imaging (MRI) and fluorescence suggest that mice deficient in LT have defective LVs. It is not known how LT contributes to lymphangiogenesis. Two hypotheses will be tested. Hypothesis I. Lymphatic vessels are regulated by LT in inflammation and development; Hypothesis II. Continual signaling through LT is necessary for maintenance and function of lymphoid organs particularly in respect to HEVs and LVs. The specific aims are to: 1. Determine how HEVs and LVs are regulated in acute inflammation by determining if B cells produce the LT ligand that regulates HEVs and LVs, by evaluating the role of macrophages in lymphangiogenesis, and by determining if the double positive vessels represent LVs budding from HEVs; 2. Determine how HEVs and LVs are regulated in chronic inflammation by evaluating vessel phenotype, density, and function, the role of macrophages, and LTbR and TNFR signaling; 3. Determine if and how LT influences constitutive LVs by evaluating LV function and phenotype 4. Determine if continual LT signaling is necessary to maintain HEVs and LVs in TLOs by treatment with LTbR and TNFR inhibitors and by turning LT on and off with a tetracycline inducible system. Elucidation of HEV and LV regulation will provide strategies for their inhibition in autoimmunity and allow control of insulitis.