Utsuyama M, Kasai M, Kurashima C, Hirokawa K
Department of Immunopathology, Tokyo Metropolitan Institute of Gerontology, Japan.
Mech Ageing Dev. 1991 May;58(2-3):267-77. doi: 10.1016/0047-6374(91)90098-k.
Three kinds of experiments were performed to see the differential effect of aging thymus on T cell differentiation in nude mice and thymectomized mice. In the experiment of thymus grafting into nude mice, the thymic capacity to promote T cell differentiation was the highest at newborn stage, and declined to 80% of the peak level at as early as 1 week of age. The level at 4 weeks of age was 50-60% of the peak level and did not greatly change thereafter with advancing age of thymus donors, up to 24 months of age. However, composition of T cell subsets differed with age of thymus graft; i.e. L3T4(CD4)+ T cells were more easily induced than Lyt-2(CD8)+ T cells by aging thymus, resulting in an increase of the ratio of L3T4+/Lyt-2+ T cells with advancing age of thymus donors. The decreased number of T cells and their subsets in the mice thymectomized at 4 weeks of age could be almost totally recovered by the grafting of newborn thymus, but less efficiently by the grafting of 24-month-old thymus. In the latter case again, L3T4+ T cells were more easily induced than Lyt-2+ T cells, resulting in an increase of the ratio of L3T4+/Lyt-2+ T cells by the grafting of the old thymus. In neonatal mice thymectomized 3 days after the birth, Lyt-2+ T cells were more severely affected than L3T4+ cells, resulting in high ratio of L3T4+/Lyt-2+ T cells. It was suggested that the capacity of the thymus to induce T cells started to decline as early as 1 week of age and did not greatly change between 4 weeks and 24 months of age. However, the composition of T cell subsets induced by the thymus changed with age, with preference for L3T4+ T cells over Lyt-2+ T cells.
进行了三种实验，以观察衰老胸腺对裸鼠和胸腺切除小鼠T细胞分化的不同影响。在将胸腺移植到裸鼠的实验中，胸腺促进T细胞分化的能力在新生阶段最高，早在1周龄时就降至峰值水平的80%。4周龄时的水平为峰值水平的50 - 60%，此后随着胸腺供体年龄的增长，直至24月龄，该水平变化不大。然而，T细胞亚群的组成随胸腺移植的年龄而不同；也就是说，衰老的胸腺更容易诱导L3T4(CD4)+ T细胞而非Lyt-2(CD8)+ T细胞，导致随着胸腺供体年龄的增长，L3T4+/Lyt-2+ T细胞的比例增加。4周龄时胸腺切除的小鼠中T细胞及其亚群数量的减少，通过移植新生胸腺几乎可以完全恢复，但移植24月龄的胸腺则效果较差。在后一种情况下，同样是L3T4+ T细胞比Lyt-2+ T细胞更容易被诱导，导致移植老龄胸腺后L3T4+/Lyt-2+ T细胞的比例增加。在出生后3天胸腺切除的新生小鼠中，Lyt-2+ T细胞比L3T4+细胞受到的影响更严重，导致L3T4+/Lyt-2+ T细胞比例较高。有人提出，胸腺诱导T细胞的能力早在1周龄时就开始下降，在4周龄至24月龄之间变化不大。然而，胸腺诱导的T细胞亚群组成随年龄而变化，相对于Lyt-2+ T细胞，更倾向于L3T4+ T细胞。
