Ma D D, Ho A H, Hoffbrand A V
Clin Exp Immunol. 1984 Feb;55(2):273-80.
Incubation with thymosin fraction 5, (TMS F5 at 300 micrograms/ml) a partially purified thymic factor, reduced the steroid binding activity of human infant thymocytes from 9.6 +/- 2.1 fmole/ml to 5.0 +/- 2.0 fmole/ml. The glucocorticoid receptor activity in normal infant thymocytes was found to be 2,146 +/- 726 (s.d.) sites per cell with dissociation constant of 1.4 +/- 0.6 X 10(-8)M. TMS F5 also increased the resistance of human thymocytes to the cytolytic effect of dexamethasone (2.5 X 10(-8)M) to 168.6 +/- 30.2% of control (P less than 0.01). In animals, medullary and peripheral blood T cells are more resistant to glucocorticoids than immature thymic T cells. The results show that thymosin can induce changes consistent with differentiation in human thymocytes. These in vitro results are consistent with a physiological role of thymosin in intrathymic T cell maturation in man. Incubation of a human malignant thymus derived T cell line (MOLT 3) with TMS F5 also resulted in a significant reduction of the number of steroid binding sites to 44.2 +/- 15.3% of control (P less than 0.05), but TMS F5 did not significantly reduce the glucocorticoid sensitivity of MOLT 3 cells.
用胸腺素组分5（TMS F5，浓度为300微克/毫升，一种部分纯化的胸腺因子）孵育后，人类婴儿胸腺细胞的类固醇结合活性从9.6±2.1飞摩尔/毫升降至5.0±2.0飞摩尔/毫升。正常婴儿胸腺细胞中的糖皮质激素受体活性为每个细胞2,146±726（标准差）个位点，解离常数为1.4±0.6×10⁻⁸M。TMS F5还增强了人类胸腺细胞对2.5×10⁻⁸M地塞米松细胞溶解作用的抗性，达到对照的168.6±30.2%（P<0.01）。在动物中，髓质和外周血T细胞比未成熟的胸腺T细胞对糖皮质激素更具抗性。结果表明，胸腺素可诱导人类胸腺细胞发生与分化一致的变化。这些体外实验结果与胸腺素在人类胸腺内T细胞成熟过程中的生理作用相符。用人恶性胸腺来源的T细胞系（MOLT 3）与TMS F5孵育，也导致类固醇结合位点数量显著减少至对照的44.2±15.3%（P<0.05），但TMS F5并未显著降低MOLT 3细胞对糖皮质激素的敏感性。
