REGULATION OF LYMPHOCYTE PROLIFERATION AND REPLICATIVE CAPACITY

淋巴细胞增殖和复制能力的调节

• 批准号: 6100990
• 负责人: R J HODES
• 金额: --
• 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/6100990
• 关键词: DNA directed DNA polymerase; cell cycle; cell differentiation; enzyme activity; enzyme induction /repression; helper T lymphocyte; human tissue; immunogenetics; immunologic memory; immunoregulation; leukopoiesis; lymphocyte proliferation; restriction fragment length polymorphism; restriction mapping; telomerase; telomere; tissue /cell culture

The replicative history and replicative potential of human naive and memory T cells, critical parameters of lymphocyte biology, were analyzed. Telomeres are unique terminal chromosomal structures which shorten with cell division in vitro and with increased age in vivo for human somatic cells. We assessed telomere length as a measure of the in vivo replicative history of naive and memory human T cells, and found that telomeric terminal restriction fragments were 1.4 q 0.1 kb longer in CD4+ naive T cells than in memory cells from the same donors, a relationship that was constant over a wide range of donor age. This suggests that the differentiation of memory cells from naive precursors occurs with substantial clonal expansion that is similar over a wide age range. The in vitro replicative capacity of naive cells was 128-fold greater than that of memory cells from the same donors. Human CD4+ naive and memory cells thus differ in in vivo replicative history as reflected in telomeric length as well as in their residual replicative capacity. These relationships may be significant for pathologies such as HIV infection, in which CD4+ T cell generation may be compromised, and for therapeutic interventions mediated by cells whose in vivo expansion is essential for therapeutic effect. Analysis of telomere length regulation in human B cells demonstrated that germinal center(GC)B cells have significantly longer telomeres than the naive B cells that are their precursors or the memory B cells that are their progeny. These results suggest the novel possibility that normal somatic cells of the B lymphocyte lineage express a mechanism capable of extending telomere length. Such a mechanism might function to extend the capacity for clonal expansion of memory and effector B cells. Telomerase, a ribonucleoprotein enzyme that is capable of synthesizing telomeric repeats, is expressed in germline and malignant cells and is absent in most normal human somatic cells. The selective expression of telomerase has thus been proposed to be a basis for the immortality of the germline and of malignant cells. When telomerase activity was analyzed in normal human T lymphocytes, it was found that telomerase is expressed at a high level in thymocytes, at an intermediate level in tonsil T cells, and at a low to undetectable level in peripheral blood T cells. Moreover, telomerase activity was highly inducible in peripheral T lymphocytes by activation through CD3 and CD28 (anti- CD3/CD28). Telomerase may thus play a permissive role in T cell development and in determining the capacity of lymphoid cells for clonal expansion. In differentiating human tonsil B cells, it was demonstrated that telomerase is expressed specifically at a high level in GC B cells. Expression of telomerase in these cells may provide a mechanism for the apparent telomere lengthening that occurs in differentiation from precursor to GC B cells. A model system has been established for analysis of the genetic regulation of telomere length in mice. Inter-fertile species of mice were identified which differ significantly in telomere length. Crosses between these species have in initial experiments demonstrated that 1) a mechanism exists for substantial telomere lengthening in somatic cells in vivo, and 2) that species-specific telomere length is regulated by segregating genes that are polymorphic between these species.

人类幼稚细胞的复制历史和复制潜力， 记忆T细胞，淋巴细胞生物学的关键参数， 分析了端粒是独特的染色体末端结构， 在体外随着细胞分裂而缩短，在体内随着年龄的增加而缩短 人体细胞我们评估了端粒长度作为衡量基因表达的指标。 体内复制历史的幼稚和记忆人类T细胞，并发现 端粒末端限制性片段长1.4q0.1kb， 在来自相同供体的CD 4+幼稚T细胞中， 这种关系在广泛的供体年龄范围内是恒定的。这 提示记忆细胞从幼稚前体细胞分化 发生大量的克隆扩张，这是类似的广泛的年龄 范围幼稚细胞的体外增殖能力为128倍 大于来自相同供体的存储器单元。人CD 4+初始 因此，记忆细胞在体内复制历史中不同， 端粒长度以及剩余复制能力。 这些关系可能对HIV等病理学具有重要意义 感染，其中CD 4 + T细胞生成可能受到损害，并且 由细胞介导的治疗干预，所述细胞的体内扩增是 对治疗效果至关重要。 人B细胞端粒长度调控分析 生殖中心（GC）B细胞的端粒明显长于 幼稚B细胞是它们的前体，记忆B细胞 是他们的后代这些结果表明了一种新的可能性， B淋巴细胞系的正常体细胞表达一种机制， 能够延长端粒长度。这种机制可能会发挥作用 以扩展记忆和效应子B的克隆扩增能力 细胞 端粒酶，一种核糖核蛋白酶，能够合成 端粒重复序列在生殖细胞和恶性细胞中表达， 在大多数正常人体细胞中不存在。的选择性表达 因此，端粒酶被认为是永生的基础。 生殖细胞和恶性细胞。当端粒酶活性 在正常人T淋巴细胞中分析，发现端粒酶是 在胸腺细胞中以高水平表达， 扁桃体T细胞，并且在外周血中处于低至检测不到的水平 T细胞。此外，端粒酶活性是高度可诱导的， 通过CD 3和CD 28（抗- CD3/CD28）。因此，端粒酶可能在T细胞中起允许作用。 发展和确定淋巴细胞的克隆能力 扩张. 在人扁桃体B细胞的分化中，证明了 端粒酶在GC B细胞中以高水平特异性表达。 端粒酶在这些细胞中的表达可能提供了一种机制， 端粒明显延长，发生在分化， GC B细胞的前体。 建立了遗传分析模型系统， 小鼠端粒长度的调节。互育种属小鼠 在端粒长度上有显著差异。十字架 在这些物种之间的初步实验表明，1） 体细胞中存在一种端粒显著延长的机制 2）物种特异性端粒长度受 分离这些物种之间的多态基因。