Receptor Mediated T and B Cell Activation

受体介导的 T 细胞和 B 细胞激活

• 批准号: 8937673
• 负责人: RICHARD J. HODES
• 金额: $ 45.9万
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8937673
• 关键词: ATM deficient; Address; Affect; Antibody Formation; Antigens; Autoimmune Responses; B-Cell Activation; B-Lymphocytes; Binding; Biochemical; Bypass; CD28 gene; CD80 gene; CTLA4 gene; Cell Cycle; Cell Death; Complex; Cytokine Receptors; Defect; Development; Distal; Family; Genetic; Human; IL2 gene; Immunoglobulin Class Switching; Immunotherapy; Incidence; Infectious Agent; Interleukin-2; LCP2 gene; Ligands; Lymphocyte; Mature T-Lymphocyte; Mediating; Messenger RNA; Molecular; Mus; Mutation; Pathway interactions; Phenotype; Play; Population; Protein p53; Role; Signal Pathway; Signal Transduction; Specificity; Staging; Structure-Activity Relationship; T cell response; T memory cell; T-Cell Activation; T-Cell Development; T-Cell Proliferation; T-Lymphocyte; Testing; Thymic Lymphoma; Transgenes; Transgenic Organisms; Translating; Tyrosine; Wild Type Mouse; base; cytokine; in vivo; mdm2 protein; member; memory CD4 T lymphocyte; mutant; novel strategies; prevent; promoter; protein expression; receptor; research study; response; selective expression; src-Family Kinases; tumor

Costimulatory B7 molecules (B7-1 or CD80; and B7-2 or CD86) are known to bind to T cell costimulatory receptors CD28 and CTLA4. Engagement of CD28 is know to transduce signals in T cells that play a critical role in T cell activation. TCR mediated activation of T cells to proliferation and IL2 secretion was enhanced in mice deficient in the adapter molecule cbl-b, suggesting a negative regulatory role for cbl-b under these conditions. Cbl-b deletion in fact reversed the inability of CD28-deficient mice to generate T cell-dependent Ig class switched primary and secondary antibody responses. The observation that cbl-b inactivation can enhance T cell responses to TCR signaling, and can bypass requirements for CD28 costimulation has been translated to studies of tumor rejection. Inactivation of cbl-b enhances the ability of mice to reject tumors that do not express costimulatory ligands (CD80 or CD86), and that grow progressively in wild type mice. Cbl-b inactivation also dramatically inhibits the incidence of thymic lymphomas in ATM-deficient mice. These findings identify a novel strategy for enhancing T cell-mediated tumor immunotherapy by modulating regulatory influences on T cell activation. The relationship between members of the cbl family and other critical adapter molecules has been studied. Experiments have indicated that inactivation of c-cbl (but not cbl-b) completely reverses the lethal phenotype caused by SLP-76 deficiency. In addition, c-cbl inactivation partially reverses the defect in T cell development caused by deficiency in SLP-76, LAT,or Vav1. These findings indicate an unanticipated SLP-76 (and LAT) independent signaling pathway that is facilitated by c-cbl inactivation. The biochemical basis for these effects has been studied using SLP-76 mutants to dissect the structure-function relationships in this pathway. C-cbl specifically rescues the T cell developmental defect resulting from SLP-76 mutations that disrupt tyrosines involved in binding to Vav and Itk. Subsequent analysis has further indicated that c-cbl inactivation rescues the developmental defect in Vav1-deficient mice, further characterizing a SLP-76/LAT/Vav1 pathway for T cell development. In contrast, c-cbl inactivation fails to overcome the T cell developmental defects that occur un lck-deficient mice. Thus, the pathways unmasked by c-cbl deficiency appear to require lck. The molecular components of this pathway are currently under study. The src family kinase lck plays a critical role in T lymphocyte development and activation. Expression of lck is regulated by two promoters, termed distal and proximal promoters, in both mice and humans. Although the existence of these promoters was desribed 20 years ago, their function in developing and mature T cels has not been analyzed. To address this question, we have generated mutant BAC transgenes by deletion of either proximal or distal lck promoter. Studies of these mice have demonstrated selective expression of lck at preferential and different stages of development when driven by one or the other of its two promoters. Corresponding slective stages of T cell development and differentiation have been shown to be dependent upon promoter-specific lck expression. We have made the unexpected observation that antigen-specific proliferative responses of naive and memory CD4 T cells require the down-modulation of tumor suppressor p53. In the absence of TCR signal, IL-2 induces a sustained increase in p53 protein, which prevents proliferative responses despite strong signaling through the IL-2 receptor. In contrast, TCR signaling results in early termination of p53 protein expression by decreasing p53 mRNA as well as by strong transcriptional induction of the p53-regulating protein Mdm2. Down-modulation of p53 in response to antigen stimulation is in fact critical for antigen-specific T cell proliferation; and preventing p53 degradation by inhibiting Mdm2 results in sustained p53 protein levels and prevents antigen-specific T cell proliferation. These studies elucidate a critical role of p53 as a negative regulator of T cell proliferation. It is the termination of p53 elevation by TCR signaling that allows proliferative responses to occur, enforcing antigen specificity.

众所周知，共刺激B7分子（B7-1或CD80； B7-2或CD86）与T细胞共刺激受体CD28和CTLA4结合。 CD28的参与度已知会在T细胞中传递信号，在T细胞激活中起着至关重要的作用。 TCR介导的T细胞对增殖和IL2分泌的激活在缺乏衔接子CBL-B中的小鼠中增强了，这表明在这些条件下，CBL-B的负调节作用为负。实际上，CBL-B删除逆转了CD28缺陷小鼠无法生成T细胞依赖性IG类切换的原代和二抗反应的无力。 CBL-B灭活可以增强T细胞对TCR信号传导的反应的观察结果，并且可以绕过CD28共刺激的要求已转化为肿瘤排斥的研究。 CBL-B的失活增强了小鼠拒绝不表达共刺激配体（CD80或CD86）的肿瘤的能力，并在野生型小鼠中逐渐生长。 CBL-B灭活还大大抑制了ATM缺乏小鼠中胸腺淋巴瘤的发生率。这些发现通过调节调节性影响T细胞激活来增强T细胞介导的肿瘤免疫疗法的新策略。已经研究了CBL家族成员与其他关键适配器分子之间的关系。实验表明，C-CBL（但不是CBL-B）的灭活完全逆转了由SLP-76缺乏引起的致命表型。此外，C-CBL失活部分逆转了由SLP-76，LAT或VAV1缺陷引起的T细胞发育中的缺陷。这些发现表明意外的SLP-76（和LAT）独立的信号通路，该通路通过C-CBL灭活促进。已经使用SLP-76突变体研究了这些作用的生化基础，以剖析该途径中的结构功能关系。 C-CBL特异性地挽救了由SLP-76突变引起的T细胞发育缺陷，这些突变破坏了与VAV和ITK结合的酪氨酸。随后的分析进一步表明，C-CBL失活挽救了VAV1缺陷型小鼠的发育缺陷，进一步表征了SLP-76/LAT/VAV1途径用于T细胞发育。相比之下，C-CBL失活无法克服发生UNCK缺陷小鼠的T细胞发育缺陷。因此，C-CBL缺乏识别的途径似乎需要LCK。该途径的分子成分目前正在研究中。 SRC家族激酶LCK在T淋巴细胞发育和激活中起着至关重要的作用。 LCK的表达受小鼠和人类的两个启动子的调节，称为远端和近端启动子。尽管这些启动子的存在是20年前被列入的，但尚未分析它们在发展和成熟的TCEL中的功能。为了解决这个问题，我们通过缺失近端或远端LCK启动子产生了突变的BAC转基因。对这些小鼠的研究表明，当其两个启动子中的一个或另一个驱动时，在优先和不同的发育阶段中LCK的选择性表达。 T细胞发育和分化的相应切片阶段已被证明取决于启动子特异性LCK表达。我们已经意外的观察结果是，天真和记忆CD4 T细胞的抗原特异性增殖反应需要对肿瘤抑制p53进行下调。在没有TCR信号的情况下，IL-2诱导p53蛋白的持续增加，尽管通过IL-2受体进行了强信号，但仍能防止增殖反应。相反，TCR信号传导通过降低p53 mRNA以及通过强烈的p53调节蛋白MDM2的强烈转录诱导来提早终止p53蛋白表达。 p53对抗原刺激的下调实际上对于抗原特异性T细胞增殖至关重要。并通过抑制MDM2来防止p53降解会导致持续的p53蛋白水平并防止抗原特异性T细胞增殖。这些研究阐明了p53作为T细胞增殖的负调节剂的关键作用。这是通过TCR信号传导终止p53升高，从而实现了增殖反应，从而实现抗原特异性。