CD8 Mediated Apoptosis During T Cell Development

描述(申请人提供)：在T细胞与抗原提呈细胞(APC)的相互作用中，受体和细胞内蛋白移位到称为免疫突触(IS)的接触区。在第一个目标中，我们将研究CD8是否作为免疫突触内的辅助受体，激活外周T细胞。 在这项建议的另一个部分，我们将继续我们最近的观察，即CD8而不是CD4与抗体或MHC I类分子的交联会导致CD4+CD8+(DP)胸腺细胞的快速凋亡。我们已经确定对这种CD8介导的凋亡敏感的胸腺细胞是早期DP群体，表达低水平的CD2和CD5，并且是CD69-。用佛波酯、PMA或CD3抗体治疗可以阻止这种诱导细胞凋亡。我们假设，在没有TCR参与的情况下，MHC I类分子连接CD8会导致早期DP胸腺细胞亚群的死亡。此外，我们的系统可能会为未能通过阳性选择的胸腺细胞提供一个模型，据说这些胸腺细胞会因为疏忽而死亡。 在这项建议中，我们将根据三个具体目标进一步描述CD8抗体和MHC I类分子诱导DP胸腺细胞凋亡的特征：(I)确定导致CD8介导的DP胸腺细胞死亡的生化事件；(Ii)确定PMA处理或TCR参与阻止CD8介导的DP胸腺细胞死亡的机制；(Iii)确定CD8介导的死亡在生理条件下是否起作用。

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 the first Aim we will examine whether CD8 behaves as a coreceptor within the immunological synapse, for the activation of peripheral T cells. In the other component of this proposal we shall follow up on our recent observation that cross-linking of CD8, but not CD4, with antibodies or MHC class I molecules, results in rapid apoptosis of CD4+CD8+ (DP) thymocytes. We have identified the thymocytes that are susceptible to this CD8 mediated apoptosis as an early DP population that expresses low levels of CD2 and CD5 and is CD69-. Treatment with the phorbol ester, PMA, or antibodies to CD3, prevents this induction of apoptosis. We hypothesize that ligation of CD8 by MHC class I molecules in the absence of TCR engagement leads to the death of a subpopulation of early DP thymocytes. Furthermore, our system may provide a model for thymocytes that fail positive selection and are said to undergo "death by neglect". In this proposal we shall further characterize the induction of apoptosis in DP thymocytes by CD8 antibodies and MHC class I molecules according to 3 specific aims: (i) to determine the biochemical events leading to the CD8 mediated death of DP thymocytes; (ii) to determine the mechanism by which treatment with PMA, or engagement of the TCR, prevents CD8 mediated death in DP thymocytes; (iii) to determine whether CD8 mediated death functions under physiological conditions.