REGULATION AND FUNCTION OF THE CD4 GENE

成熟T淋巴细胞可以根据它们的不同分为两个亚群 表达两种细胞表面糖蛋白中的一种，即CD4或CD8。T 识别第二类主要组织相容性复合体(MHC)的细胞 蛋白质通常表达CD4，是助手或诱导者，而那些 识别第I类MHC蛋白通常表达CD8并具有细胞毒性(或 可能是抑制者)。Cd4已被证明在 增强T细胞对抗原的反应和T细胞的选择 在胸腺发育过程中。此应用程序的目标是定义 CD4完成这两个功能的机制。A CD4-CD8-，KB 反应性T细胞杂交瘤将被用来确定CD4是否可以 增强对I类MHC蛋白的反应，如果是，是否会发生这种情况 仅仅通过黏附或也通过信号转导。美国政府的角色 酪氨酸激酶p56lck在CD4介导的抗原应答增强中的作用 将通过野生型和突变型p56lck的转染法进行检测 在II类限制性抗原依赖的T细胞杂交瘤中。互动 Cd4和p56lck的构成活性形式之间的关系将被检查以 确定它们的影响是否相加，两者是否关联， 以及CD4和/或T细胞受体(TCR)的交联性对 蛋白质结合、底物和抗原的酪氨酸磷酸化 回应。TCR相关的p59fyn酪氨酸激酶在CD-4中的作用 介导的抗原反应刺激也将使用 突变型和野生型p59fyn构建。双打的机制(S) 如果胸腺细胞具有II类抗原，则阳性胸腺细胞将成为单一的CD4阳性细胞 受限TCR，或CD8，如果他们有I类受限TCR将是 探索过了。这将通过交配表达A基因的转基因小鼠来完成 CD8/CD4嵌合基因构建的I类特异性TCR转基因小鼠和 一只缺乏II类基因的小鼠。同源重组也将被使用 产生内源性CD8α基因被替换为 具有CD4跨膜区和细胞质尾巴的CD8α，或 内源性的CD4基因被反向构建的基因所取代。

Mature T lymphocytes can be divided into two subsets based upon their expression of either of two cell surface glycoproteins, CD4 or CD8. T cells that recognize class II major histocompatibility complex (MHC) proteins generally express CD4 and are helper or inducer, while those that recognize class I MHC proteins generally express CD8 and are cytotoxic (or possibly suppressor). CD4 has been shown to play important roles in enhancing T cell responses to antigen and in the selection of T cells during thymic development. The goal of this application is to define the mechanisms by which CD4 accomplishes these two functions. A CD4-CD8-, Kb responsive T cell hybridoma will be used to determine whether CD4 can enhance responses to class I MHC proteins, and if so, whether this occurs merely by adhesion or also by signal transduction. The role of the tyrosine kinase p56lck in CD4-mediated enhancement of antigen responses will be examined using transfection of wild-type and mutant forms of p56lck in a class II restricted, antigen dependent T cell hybridoma. Interactions between CD4 and a constitutively active form of p56lck will be examined to determine whether their effects are additive, whether the two associate, and the effects of cross-linking of CD4 and/or the T cell receptor (TCR) on protein associations, tyrosine phosphorylation of substrates and antigen responses. The role of the TCR-associated p59fyn tyrosine kinase in CD-4 mediated stimulation of antigen responses will also be assessed using mutant and wild-type p59fyn constructs. The mechanism(s) by which double- positive thymocytes become single positive for CD4 if they have a class II restricted TCR, or CD8 if they have a class I restricted TCR will be explored. this will be done both by mating transgenic mice expressing a chimeric CD8/CD4 construct to a class I specific TCR transgenic mouse and to a class II deficient mouse. Homologous recombination will also be used to generate mice in which the endogenous CD8alpha gene is replaced with CD8alpha having a CD4 transmembrane region and cytoplasmic tail, or the endogenous CD4 gene is replaced with the reverse construct.