Understanding affinity variation in the CD28/ CTLA-4 pathway and its impact on immune function.

CD28-CTLA-4系统是控制T细胞免疫反应的核心。虽然CD28是一种激活受体，但CTLA-4反对这种功能，抑制反应。事实上，CTLA-4功能的遗传缺陷导致自身免疫，抗体阻断用于刺激对癌症的免疫治疗。尽管它们的功能相反，CD28和CTLA-4共享两个配体CD80和CD86，这两个配体在亲和力和亲和度特征上都不同。这些不同的配体特征如何影响免疫功能尚不清楚。在这个项目中，我们建议探索配体特征的变化如何影响免疫功能。我们将生成和表征不同的配体变异，以研究它们在一系列免疫环境中的影响。抗原呈递细胞（B细胞系）将被改造以表达不同的配体，并在不同水平的配体表达下比较功能结果。我们期望在体外研究人类T细胞对不同配体组合的反应，测量它们对T细胞活化、扩增、存活、细胞表型、细胞因子产生和分化的影响。实验将在CTLA-4存在和不存在的情况下进行。此外，我们将进行研究，以测量不同的配体是如何由CTLA-4转内吞作用控制的，以及它们如何影响调节性T细胞（Treg）稳态。该项目将通过克隆和表达配体变体及其免疫功能的研究，提供分子生物学、免疫学和细胞生物学方面的培训和经验。总体而言，该项目将详细了解CD28和CTLA-4配体的生物物理特性与其对免疫细胞功能的调节之间的关系。

The CD28-CTLA-4 system is central to the control of T cell immune responses. While CD28 is an activating receptor, CTLA-4 opposes this function, inhibiting responses. Indeed, genetic deficiency in CTLA-4 function results in autoimmunity and antibody blockade is used to stimulate immunity to cancer therapeutically.Despite their opposing functions, CD28 and CTLA-4 share two ligands, CD80 and CD86, which differ in both affinity and avidity characteristics. How these distinct ligand characteristics affect immune function is not understood. In this project we propose to explore how changes in ligand characteristics impact immune function. We will generate and characterize different ligand variants in order to study their impact in a range of immune settings.Antigen presenting cells (B cell lines) will be engineered to express different ligands and functional outcomes will be compared at different levels of ligand expression. We anticipate studying human T cell responses to different ligand combinations in vitro, measuring their effect on T cell activation, expansion, survival, cellular phenotype, cytokine production and differentiation. Experiments will be carried out both in the presence and absence of CTLA-4 expression. In addition, we will perform studies to measure how different ligands are controlled by CTLA-4 transendocytosis and how they affect regulatory T cell (Treg) homeostasis. The project will provide training and experience in molecular biology, immunology and cell biology via the cloning and expressing of ligand variants and the study of their immune function. Overall, the project will generate a detailed understanding of the relationship between the biophysical characteristics CD28 and CTLA-4 ligands and their regulation of immune cell function.