CD28 MEDIATED ACTIVATION SIGNALS

抗原特异性T淋巴细胞活化的双信号模型目前已被广泛应用于临床， 被广泛接受。 在该模型中，第一信号由下式提供： TCR的抗原特异性活化。 提供第二个共同- 不通过抗原特异性T细胞介导的刺激信号 受体是激活静息幼稚T细胞和T细胞活化所必需的。 导致IL-2产生的克隆。 T细胞分子CD 28介导 T细胞的共刺激信号。 因此，CD 28在以下方面发挥作用： T细胞无反应性的发展和抗原的发展- 具体宽容。我们最近提出了几个重要的意见 关于CD 28介导的信号。首先，CD 28 CYT含有 PI 3激酶SH 2结合基序和CD 28连接导致 - PI 3激酶与CD 28 CYT的结合和PI 3激酶的活化。第二、 我们观察到CD 28交联导致酪氨酸 磷酸化和激活tec酪氨酸激酶EMT/ITK， 第三，鸟嘌呤核苷酸交换因子vav变成酪氨酸 在CD 28连接后不久磷酸化。 我们还证明 人白血病NK细胞系YT，其为CD 28+，可用于 评价CD 28介导的细胞溶解效应机制的活化。 我们的初步数据表明，特定的Pi 3激酶抑制剂具有 对CD 28介导的细胞溶解效应子功能的显著影响。 此外，CD 28介导的信号上调并激活整合素 （LFA-1和VLA-4）对Jurkat细胞系的作用，以及改变LFA-1和VLA-4中的酪氨酸。 在CD 28细胞色素T中，173位的苯丙氨酸消除了CD 28介导的 整合素功能的上调。 这些研究将进一步 在提案中延伸。 具体目标是：（1）确定 CD 28信号传输对CD 28 CYT的最低要求 在CD 28交联之后。这些研究将集中在酪氨酸 磷酸化模式、IL-2产生和LFA-1活化。 的 将使用CD 28 CYT缺失突变体和替代进行分析 CD 28 CYT中的酪氨酸突变。 (2)为了确定PI 3-激酶 与CD 28 CYT的结合是CD 28介导的信号转导所必需的 导致细胞溶解效应子功能。 (3)为了确定结构 EMT激酶和CD 28细胞色素T之间的相互作用位点和EMT- CD 28介导的激活信号的显性负突变。 这些 研究将描述CD 28活化的下游效应。

The two signal model for antigen-specific T lymphocyte activation has now been widely accepted. In this model the first signal is provided by antigen-specific activation of the TCR. The provision of a second co- stimulatory signal which is not mediated via the antigen-specific T cell receptor is necessary for activation of resting naive T cells and T cell clones leading to IL-2 production. The T cell molecule CD28 is mediating co-stimulatory signals for T cells. CD28 therefore plays a role in development of T cell unresponsiveness and development of antigen- specific tolerance. We have recently made several important observations concerning CD28 mediated signals. The first is that the CD28CYT contains the SH2 binding motif for PI3 kinase and that CD28 ligation results in binding of- PI3 kinase to CD28CYT and activation of PI3 kinase. Secondly, we made the observation that CD28 crosslinking results in tyrosine phosphorylation and activation of the tec tyrosine kinase EMT/ITK and thirdly, that the guanine nucleotide exchange factor vav becomes tyrosine phosphorylated shortly after CD28 ligation. We have also demonstrated that the human leukemic NK cell line YT, which is CD28+ can be used for evaluating CD28 mediated activation of cytolytic effector mechanisms. Our preliminary data demonstrate that specific Pi3 kinase inhibitors have a dramatic effect on CD28 mediated cytolytic effector function. furthermore, CD28 mediated signals upregulate and activate integrins (LFA-1 and VLA-4) on the Jurkat cell line, and changing tyrosine in position 173 to phenylalanine in the CD28CYT abolishes the CD28 mediated upregulation of integrin function. These studies will be further extended in the proposal. The specific aims are: (1) To determine the minimal requirements of CD28CYT for transmission of CD28 signals following CD28 crosslinking. These studies will focus on tyrosine phosphorylation patterns, IL-2 production and LFA-1 activation. The analysis will be performed using CD28CYT deletion mutant and substitution mutations of tyrosines in the CD28CYT. (2) To determine if PI3-kinase binding to CD28CYT is essential for CD28 mediated signal transduction leading to cytolytic effector function. (3) To determine the structural interaction sites between EMT kinase and CD28CYT and the effects of EMT- dominant negative mutations on CD28 mediated activation signals. These studies will delineate the downstream effects of CD28 activation.