REGULATION OF LYMPHOCYTE PROLIFERATION AND REPLICATIVE CAPACITY

人类幼稚的复制历史和复制潜力 记忆T细胞是淋巴细胞生物学的关键参数 分析过了。端粒是一种独特的末端染色体结构， 在体外随着细胞分裂而缩短，在体内随年龄增加而缩短 人类体细胞。我们评估了端粒长度作为一种测量端粒长度的方法 活体复制幼稚和记忆性人类T细胞的历史，并发现 端粒末端限制性片段长1.4q0.1kb 与来自相同捐赠者的记忆细胞相比，在CD4+初始T细胞中， 这种关系在广泛的捐赠者年龄范围内是恒定的。这 表明记忆细胞从幼稚的前体细胞分化而来 发生大量的克隆扩张，这种扩张在很长一段时间内都是相似的 射程。幼稚细胞的体外复制能力是128倍 比来自相同捐赠者的记忆细胞的数量要大。人类CD4+幼稚 因此，正如所反映的那样，记忆细胞在体内的复制历史上不同 端粒长度以及它们的剩余复制能力。 这些关系可能对艾滋病毒等病理疾病具有重要意义 感染，在这种感染中，CD4+T细胞的产生可能受到影响， 体内扩增的细胞介导的治疗干预 对于治疗效果来说是必不可少的。 人类B细胞端粒长度调节分析证实 生发中心(GC)B细胞的端粒明显比 幼稚的B细胞是它们的前体，或者是记忆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 能够延长端粒长度的。这样的机制可能会发挥作用 扩大记忆和效应器B的克隆扩展能力 细胞。 端粒酶，一种核糖核蛋白酶，能够合成 端粒重复序列，在生殖系和恶性细胞中表达，是 在大多数正常人的体细胞中不存在。基因的选择性表达 因此，端粒酶被认为是长生不老的基础 生殖系和恶性细胞。当端粒酶活性在 对正常人T淋巴细胞的分析发现，端粒酶是 在胸腺细胞中高水平表达，在 扁桃体T细胞，以及外周血中低至检测不到的水平 T细胞。此外，端粒酶活性在 通过CD3和CD28激活的外周T淋巴细胞(抗CD28) CD3/CD28)。端粒酶可能因此在T细胞中发挥许可作用 淋巴样细胞的发育及其克隆能力的测定 扩张。 在分化人类扁桃体B细胞的过程中，已经证明 端粒酶在GC B细胞中高水平表达。 端粒酶在这些细胞中的表达可能提供了一种机制 分化过程中出现的明显端粒延长 GC B细胞的前体。 建立了用于遗传分析的模型系统 小鼠端粒长度的调节。可生育的小鼠种类 在端粒长度上有显著差异。十字架 这些物种之间的关系在初步实验中证明了1) 体细胞中存在一种显著延长端粒的机制 以及2)物种特异性端粒长度受 分离这些物种之间的多态基因。

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.