CD8 in the Immunological Synapse and in Thymocyte Death

描述（由申请人提供）：在T细胞与抗原呈递细胞（APC）相互作用期间，受体和细胞内蛋白质移位到称为免疫突触（IS）的接触区域。在CD 4 T细胞中，通过增加抗原肽的量，可以容易地使IS形成不依赖于CD 4，而对于CD 8 T细胞则不是如此。此外，CD 4迅速移出IS中心，而我们没有观察到任何这样的CD 8清除。在这个提议中，我们将研究与APC相互作用的CD 8 T细胞的IS。特别是，我们将集中在CD 4/8共受体的要求和抗原性和非抗原性MHC I类分子的运动。我们还将研究在CD 8介导的、TCR独立的与APC的相互作用过程中，未成熟胸腺细胞中SMAC的形成。 已经证明，MHC I四聚体可以以TCR非依赖性方式与DP胸腺细胞上的CD 8结合。该结合事件归因于与CD 8单阳性胸腺细胞和外周T细胞相比，DP胸腺细胞上CD 8糖基化的发育调节差异。相反，没有证据表明MHC II类四聚体与DP胸腺细胞上的CD 4的TCR独立结合。尚未确定该事件的影响和/或生物学相关性。最近，我们发现抗体介导的CDS交联，而不是CD 4，导致CD 4-CD 8（DP）胸腺细胞的快速凋亡。用佛波醇酯PMA处理可防止由CD 8交联引起的细胞凋亡的诱导。我们推测，在没有TCR参与的情况下，CD 8通过生理配体的连接导致T细胞发育期间DP胸腺细胞的死亡。 在本申请中，我们将进一步表征CD 8抗体诱导DP胸腺细胞凋亡，并研究经典或非经典MHC I类分子是否可以以TCR非依赖性方式诱导DP胸腺细胞凋亡。这些研究将包括4个具体目标：（1）确定CD 8是否作为免疫突触内的辅助受体，用于活化外周T细胞;（2）确定导致DP胸腺细胞中CD 8介导的死亡的生化事件;（3）确定PMA治疗预防DP胸腺细胞中CD 8介导的死亡的机制;（4）确定CD 8介导的死亡是否具有生理功能。

DESCRIPTION (provided by applicant): During the interaction of T cells with antigen presenting cells (APCs), receptors and intracellular proteins translocate into the contact region known as the Immunological Synapse (IS). In CD4 T cells IS formation can readily be rendered independent of CD4 by increasing the amount of antigenic peptide whereas the same does not hold true for CD8 T cells. In addition, CD4 rapidly moves out of the center of the IS whereas we do not observe any such clearance of CD8. In this proposal we shall examine the IS of CD8 T cells interacting with APCs. In particular we shall focus on the requirement of the CD4/8 co-receptor and on the movement of both antigenic and non-antigenic MHC class I molecules. We shall also examine SMAC formation in immature thymocytes during a CD8 mediated, TCR independent interaction with APCs. It has been demonstrated that MHC I tetramers can bind to CD8 on DP thymocytes in a TCR independent manner. This binding event has been attributed to a developmentally regulated difference in the glycosylation of CD8 on DP thymocytes compared to CD8 single positive thymocytes and peripheral T cells. In contrast there is no evidence for TCR independent binding of MHC class II tetramers to CD4 on DP thymocytes. The implications and/or biological relevance of this event have not been determined. Recently we have found that antibody mediated cross-linking of CDS, but not CD4, results in rapid apoptosis of CD4 CD8 (DP) thymocytes. Treatment with the phorbol ester, PMA, prevents the induction of apoptosis resulting from CD8 cross-linking. We hypothesize that the ligation of CD8 by physiological ligands in the absence of TCR engagement leads to the death of DP thymocytes during T cell development. In this application we shall further characterize the induction of apoptosis in DP thymocytes by CD8 antibodies and also investigate whether classical or non-classical MHC class I molecules can induce apoptosis in DP thymocytes in a TCR independent manner. These studies will incorporate 4 specific aims: (1) To determine whether CD8 behaves as a co-receptor within the immunological synapse, for the activation of peripheral T cells (2) To determine the biochemical events leading to the CD8 mediated death of DP thymocytes; (3) To determine the mechanism by which treatment with PMA prevents CD8 mediated death in DP thymocytes; (4) To determine whether CD8 mediated death has a physiological function.