Hirokawa K, Utsuyama M, Katsura Y, Sado T
Department of Pathology, Tokyo Metropolitan Institute of Gerontology, Japan.
Arch Pathol Lab Med. 1988 Jan;112(1):13-21.
Bone marrow cells obtained from B10.Thy-1.1 mice (H-2b, Thy-1.1) were injected directly into the thymus of C57BL/6 mice (H-2b,Thy 1.2) of various ages. Thymocyte precursors in the injected donor-bone marrow cells could proliferate in the thymic microenvironment in the following manner: first, preferentially proliferating into the subcapsular cortex; and second, spreading to the whole layer of the cortex, a portion of them gradually moving into the medulla. The proliferation of donor-type thymocytes was most pronounced when intrathymic injection of bone marrow cells (ITB) was performed in newborn mice and especially prominent in week-old mice; it took approximately ten weeks for donor-type thymocytes to finish the whole course of proliferation, differentiation, and emigration to the periphery. When ITB was performed in mice 4 weeks of age and older, the proliferation of donor-type thymocytes was retarded at onset, less pronounced in magnitude, and disappeared earlier. Emigration of donor-type T cells from the thymus to the peripheral lymphoid tissues occurred most rapidly when ITB was performed in newborn mice, and these T cells continued to reside thereafter in the peripheral lymphoid tissues. However, when ITB was performed in mice 4 weeks of age and older, the number of emigrated T cells in the spleen decreased (about a tenth of that in newborn mice) and, moreover, these T cells resided only transiently in the spleen. It was suggested that T cells emigrating from the thymus of mice from newborn to 2 weeks of age are long-lived, whereas those from the thymus in mice 4 weeks of age and older are short-lived. However, when 4-week-old young adult mice were treated by irradiation or hydrocortisone, the thymic capacity was enhanced in terms of proliferation and peripheralization of thymocytes, and emigrated T cells became long-lived.
从B10.Thy-1.1小鼠（H-2b，Thy-1.1）获取的骨髓细胞被直接注射到不同年龄的C57BL/6小鼠（H-2b，Thy 1.2）的胸腺中。注射的供体骨髓细胞中的胸腺细胞前体可以以下方式在胸腺微环境中增殖：首先，优先增殖至被膜下皮质；其次，扩散至整个皮质层，其中一部分逐渐移入髓质。当在新生小鼠中进行胸腺内骨髓细胞注射（ITB）时，供体型胸腺细胞的增殖最为明显，在1周龄小鼠中尤其显著；供体型胸腺细胞完成增殖、分化并迁移至外周大约需要十周时间。当在4周龄及以上的小鼠中进行ITB时，供体型胸腺细胞的增殖在开始时受到抑制，增殖程度较低，且消失得更早。当在新生小鼠中进行ITB时，供体型T细胞从胸腺迁移至外周淋巴组织的速度最快，并且这些T细胞此后继续驻留在外周淋巴组织中。然而，当在4周龄及以上的小鼠中进行ITB时，脾脏中迁移出的T细胞数量减少（约为新生小鼠的十分之一），此外，这些T细胞仅短暂驻留在脾脏中。有人提出，从新生至2周龄小鼠胸腺中迁移出的T细胞是长寿的，而从4周龄及以上小鼠胸腺中迁移出的T细胞是短寿的。然而，当对4周龄的年轻成年小鼠进行照射或氢化可的松处理时，胸腺细胞在增殖和外周化方面的胸腺能力增强，并且迁移出的T细胞变得长寿。
