TRANSPLANTATION ANTIGENS--EXPRESSION AND FUNCTION

高度多态的经典移植的功能 在移植排斥反应和对病毒感染的防御中有抗原 很久以前就被公认了。相比之下，属性和 非多态类大家族的生理效应 像我一样的MHC分子仍然是未知的。结构上的相似之处 这两类多肽表明非经典的MHC 分子可能与自体或非自体多肽结合，也可能与T细胞相互作用 感受器。推定的蛋白质的鉴定 多肽的派生和对它们可能影响的认识 与之相互作用的细胞上存在着重大挑战，因为它们 可能导致免疫学中新概念的形成。 Qa-2分子是最典型的非经典分子之一。 小鼠体内的移植抗原。它们以两种形式存在：1) 糖磷脂-肌醇(GPI)连接的膜抗原 主要表达在淋巴来源的细胞上，并可用作 细胞毒细胞和激活信号转导的靶标 和2)可溶的Qa-2分子释放到T细胞中 血清，并已被假设诱导激活或无能状态。 从膜到可溶性形式的“转换”在体外可以通过以下方式诱导 细胞激活，涉及QA-2外显子5的选择性剪接 吉恩。 这项建议的具体目标是： 1.鉴定控制Qa-2基因的顺式作用元件 外显子5的选择性剪接。 2.检验不同的养生方式和信号诱导的假设 免疫系统的激活(即，导致选择性剪接 体内Qa-2mRNA和可溶性Qa-2分子的分泌，以及 确定主要参与Qa-2表达的细胞亚群 不同的反应。 3.对与分泌型和GPI连接的Qa-2结合的多肽进行测序 分子，以识别由病毒呈现的自身抗原 两个Qa-2亚型，并对高度 纯化的Qa-2蛋白，以解决三维结构的 非经典MHC抗原。 目标1和目标2中提出的研究将促进对 真核生物可诱导选择性剪接的一般机制 基因，并将提供特定条件和细胞的信息 免疫应答过程中与偏爱相关的亚群 生产可溶性或GPI连接的QA-2产品。这些数据可能会允许 来定义Qa-2亚型的生理功能。研究 在目标3中，将直接检测与这些蛋白质结合的多肽，并 将评估Qa-2多肽与经典多肽的结构相似性 移植抗原。结果将被用来推断 Qa-2分子呈递的抗原和所需的参数 MHC分子与蛋白质片段的结合。 从长远来看，拟议的研究可能有助于设计疫苗， 防止自身免疫和操纵MHC识别过程。

The functions of the highly polymorphic classical transplantation antigens in graft rejection and in defense against viral infections have long been well recognized. In contrast, the properties and the physiological effects of the much larger family of nonpolymorphic class I-like MHC molecules are still unknown. The structural similarities of the two classes of polypeptides suggest that the nonclassical MHC molecules may bind self or nonself peptides and may interact with T-cell receptors. The identification of the proteins from which the putative peptides are derived and the recognition of the effects that they may have on cells with which they interact represent major challenges as they may lead to the formulation of new concepts in immunology. Qa-2 molecules are among the best characterized nonclassical transplantation antigens in the mouse. They exist in two forms: 1) glycophosphatidyl-inositol (GPI) linked membrane antigens which are predominantly expressed on lymphoid derived cells and can serve as targets for cytotoxic cells as well as transducers of activation signals in T cells and 2) soluble Qa-2 molecules which are released into the serum and have been hypothesized to induce activation or anergy states. The "switching" from membrane to soluble form is inducible in vitro by cell activation and involves alternative splicing of exon 5 of the Qa-2 gene. The specific aims of this proposal are: 1. To identify the cis-acting elements of the Qa-2 genes that control alternative splicing of exon 5. 2. To test a hypothesis that various regimens and signals inducing activation of immune system (i.e., lead to the alternative splicing of Qa-2 mRNA and secretion of soluble Qa-2 molecules in vivo, and to identify the major Qa-2 expressing cell subsets participating in different responses. 3. To sequence the peptides bound to the secreted and GPI-linked Qa-2 molecules in order to identify the self-antigens presented by the two Qa-2 isoforms, and to perform crystallography on the highly purified Qa-2 proteins in order to solve a 3D structure of the nonclassical MHC antigen. The studies proposed in Aims 1 and 2 will advance the understanding of the general mechanisms of inducible alternative splicing of eukaryotic genes and will provide information on specific conditions and cell subsets during immune responses that correlate with preferential production of soluble or GPI-linked Qa-2 products. These data may allow us to define the physiological functions of the Qa-2 isoforms. Studies in Aim 3 will examine directly the peptides bound to these proteins and will assess structural similarity of Qa-2 polypeptides to classical transplantation antigens. The results will be used to deduce the antigens presented by Qa-2 molecules and the parameters required for binding of protein fragments by MHC molecules. In the long term the proposed research may help to design vaccines, prevent autoimmunity and manipulate MHC recognition processes.