Thymocyte tuning after selection: mechanisms to avoid autoreactivity

选择后胸腺细胞调整：避免自身反应的机制

基本信息

批准号：
7493002
负责人：
TERRI M. LAUFER
金额：
$ 38.63万
依托单位：
UNIVERSITY OF PENNSYLVANIA
依托单位国家：
美国
项目类别：
财政年份：
2007
资助国家：
美国
起止时间：
2007-09-15 至 2011-08-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7493002
关键词：
Adoptive Transfer Affinity Antibody Formation Attenuated Autoantibodies Autoimmunity Biochemical Bone Marrow CD4 Positive T Lymphocytes Cell Lineage Cells Class Clonal Deletion Complex Data Defect Development Disease Environment Epithelial Cells Epithelium Event Generations Helper-Inducer T-Lymphocyte Hematopoietic Histocompatibility Antigens Class II Human Hyperactive behavior Immune system Ligands Lupus MHC Class II Genes Mature T-Lymphocyte Mediating Membrane Microdomains Modeling Molecular Mus Nuclear Pathogenesis Pathologic Pathway interactions Pattern Peptide/MHC Complex Peptides Phenotype Production Protein Tyrosine Kinase Receptor Signaling Relative (related person)Research Personnel Role Self Tolerance Site Stromal Cells T-Cell Activation T-Cell Receptor T-Lymphocyte Techniques Thymus Gland Transgenic Mice autoreactivity genetic regulatory protein migration mouse model novel therapeutics prevent programs research study response therapeutic target thymocyte

项目摘要

DESCRIPTION (provided by applicant): Anti-nuclear antibody production in human and murine lupus is associated with inappropriate activation of self-reactive CD4+ helper T cells. Thymic clonal deletion appears intact, suggesting that self-reactive T cells do not merely escape negative selection. We hypothesize that defects in a post-selection mechanism of T cell tolerance that we call developmental tuning contribute to the pathogenesis of lupus. To avoid autoimmunity, positive selection must be followed by a period of developmental tuning when T cell receptor (TCR) responsiveness to low affinity self-peptides is inhibited. We hypothesize that this fundamental mechanism of self-tolerance is disrupted in lupus. We recently utilized transgenic mice with restricted expression of MHC class II to demonstrate that CD4 SP thymocytes that cannot interact with MHCII after they have been selected retain the phenotype of immature cells and are hyperresponsive to TCR signaling. We proposed that developmental tuning is an active event requiring ongoing interactions between the CD4 SP thymocyte and MHC class II (MHCII) thymic medullary stroma. We now find that CD4 SP thymocytes from lupus prone mice are similarly hyperactive. We now propose to identify the molecular mechanisms regulating developmental tuning. In Specific Aim I, we will define the molecular and cellular interactions which regulate developmental tuning. First, we will determine whether MHC class II molecules are interacting with the T cell receptor or CD4 to mediate tuning. Then, we will utilize transgenic mice and bone marrow chimeraes to determine which MHC class ll-positive thymic stromal cells-medullary epithelium or hematopoietic APC-mediate CD4 SP maturation. Our data suggest that developmental tuning makes T cell activation more dependent on engagement of CD4 by increasing the allegiance of the tyrosine kinase, Lck, for CD4. In Specific Aim II, we will take a biochemical approach to determine how the subcellular localization and associations of Lck and CD4 are regulated. Finally, in the third Specific Aim we will ask if developmental tuning is disrupted in two murine models of spontaneous anti-nuclear antibody production and lupus. These experiments will define the mechanisms which regulate a critical thymic pathway that the immune system utilizes to avoid autoreactivity.

描述（由申请人提供）：人和鼠狼疮中抗核抗体的产生与自身反应性 CD4+ 辅助 T 细胞的不适当激活有关。胸腺克隆缺失看起来完整无缺，这表明自身反应性 T 细胞不仅仅逃脱了阴性选择。我们假设 T 细胞耐受的选择后机制（我们称之为发育调节）的缺陷导致了狼疮的发病机制。为了避免自身免疫，阳性选择之后必须进行一段发育调整，此时 T 细胞受体 (TCR) 对低亲和力自肽的反应受到抑制。我们假设这种自我耐受的基本机制在狼疮中被破坏。我们最近利用限制表达 MHC II 类的转基因小鼠来证明，在选择后不能与 MHCII 相互作用的 CD4 SP 胸腺细胞保留了未成熟细胞的表型，并对 TCR 信号传导过度敏感。我们提出，发育调节是一个主动事件，需要 CD4 SP 胸腺细胞和 MHC II 类 (MHCII) 胸腺髓质基质之间持续相互作用。我们现在发现来自狼疮易感小鼠的 CD4 SP 胸腺细胞同样过度活跃。我们现在建议确定调节发育调节的分子机制。在特定目标 I 中，我们将定义调节发育调节的分子和细胞相互作用。首先，我们将确定 MHC II 类分子是否与 T 细胞受体或 CD4 相互作用以介导调节。然后，我们将利用转基因小鼠和骨髓嵌合体来确定哪种MHC II类阳性胸腺基质细胞-髓质上皮或造血APC介导CD4 SP成熟。我们的数据表明，发育调节通过增加酪氨酸激酶 Lck 对 CD4 的忠诚度，使 T 细胞激活更加依赖于 CD4 的参与。在特定目标 II 中，我们将采用生化方法来确定 Lck 和 CD4 的亚细胞定位和关联是如何受到调节的。最后，在第三个具体目标中，我们将询问自发抗核抗体产生和狼疮的两种小鼠模型中的发育调节是否被破坏。这些实验将定义调节免疫系统用来避免自身反应的关键胸腺途径的机制。