Ernst D N, Weigle W O, McQuitty D N, Rothermel A L, Hobbs M V
Department of Immunology, Research Institute of Scripps Clinic, La Jolla, CA 92037.
J Immunol. 1989 Mar 1;142(5):1413-21.
Splenocytes from young (3 to 4 mo) and aged (24 to 26 mo) C57BL/6 mice were stimulated with anti-CD3 epsilon mAb in vitro. At the time of peak DNA synthesis (day 2), cells from aged mice incorporated congruent to 60% less [3H]TdR than cells from young mice. This age-related defect was not attributable to gross differences in anti-CD3 does optima, response kinetics, accessory cell function, numbers of T cells cultured, CD4+:CD8+ cell ratios or surface levels of CD3 epsilon molecules. In an attempt to analyze pre-S phase events in these responses, we monitored CD4+ and CD8+ cells in splenocyte cultures for the time-dependent expression of three T cell activation markers: RL388 Ag and IL-2R and transferrin R. Parallel analyses of mean T cell size and cell cycle phase distributions were performed. Non-activated T cells from both age groups similarly expressed moderate levels of RL388 Ag, low levels of transferrin R, and undetectable levels of IL-2R. Analysis of stimulated T cells revealed, in both age groups: 1) detectable increases in expression of all three markers by 6 h of culture, and continued increases associated with blastogenesis and G1 phase transit and 2) a preferential stimulation of the CD8+ subset to a state of high level marker expression. Age group comparisons of activation marker expression over time suggested that the age-related defect reflects proportionally smaller fractions of CD4+ and CD8+ cells that respond normally, rather than a general defect in all T cells or a subset-specific defect. Finally, we found that supernatants from aged donor cell cultures stimulated with anti-CD3 contained less Il-2 than those of young controls. Addition of an IL-2 containing supernatant to aged donor cell cultures increased, but did not restore, the S phase response on day 2; however, the response on day 3 was comparable to the peak (day 2) response of young controls. These data suggest that exogenous IL-2 can improve the aged response, perhaps by expanding the fraction of normally reactive T cells.
用抗CD3ε单克隆抗体在体外刺激年轻（3至4个月）和老年（24至26个月）C57BL/6小鼠的脾细胞。在DNA合成高峰期（第2天），老年小鼠的细胞掺入的[3H]TdR比年轻小鼠的细胞少约60%。这种与年龄相关的缺陷并非归因于抗CD3剂量最佳值、反应动力学、辅助细胞功能、培养的T细胞数量、CD4+：CD8+细胞比例或CD3ε分子表面水平的显著差异。为了分析这些反应中S期前的事件，我们监测了脾细胞培养物中CD4+和CD8+细胞三种T细胞活化标志物的时间依赖性表达：RL388抗原、IL-2受体和转铁蛋白受体。同时对平均T细胞大小和细胞周期阶段分布进行了分析。两个年龄组未活化的T细胞同样表达中等水平的RL388抗原、低水平的转铁蛋白受体和无法检测到的IL-2受体水平。对刺激的T细胞分析显示，在两个年龄组中：1）培养6小时后，所有三种标志物的表达均有可检测到的增加，并随着细胞增殖和G1期转变持续增加；2）CD8+亚群优先被刺激到高水平标志物表达状态。随着时间推移对活化标志物表达的年龄组比较表明，与年龄相关的缺陷反映出正常反应的CD4+和CD8+细胞比例成比例地较小，而不是所有T细胞普遍存在缺陷或亚群特异性缺陷。最后，我们发现用抗CD3刺激的老年供体细胞培养物的上清液中IL-2含量比年轻对照的少。向老年供体细胞培养物中添加含IL-2的上清液可增加但不能恢复第2天的S期反应；然而，第3天的反应与年轻对照的峰值（第2天）反应相当。这些数据表明，外源性IL-2可能通过扩大正常反应性T细胞的比例来改善老年反应。
