Iwata M, Mukai M, Nakai Y, Iseki R
Laboratory of Cellular Immunology, Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan.
J Immunol. 1992 Nov 15;149(10):3302-8.
Apoptosis is induced in immature thymocytes and T cell hybridomas upon stimulation via the TCR/CD3 complex. This phenomenon appears to be related to negative selection of T cell clones in the thymus. In T cell hybridomas, it has been shown that glucocorticoids inhibit TCR/CD3-mediated apoptosis, whereas glucocorticoids alone induce apoptosis. All-trans-retinoic acid (RA) at 0.1 to 10 microM also inhibited TCR/CD3-mediated apoptosis assessed by DNA fragmentation and cytolysis, but RA alone hardly induced apoptosis. RA enhanced the effects of glucocorticoids to induce apoptosis and to inhibit TCR/CD3-mediated apoptosis. TCR/CD3-mediated stimulation can be mimicked by the combination of ionomycin, a calcium ionophore, and PMA, an activator of protein kinase C, and the combination-induced DNA fragmentation was also inhibited by RA. RA, however, failed to inhibit the combination-induced increase in intracellular Ca2+ concentration or the combination-induced translocation of protein kinase C from the cytosolic fraction to the particulate fraction. Time course studies of RA addition into the culture indicated that a 3- to 6-h delay in the addition of RA did not reduce its inhibitory effect on anti-CD3-induced DNA fragmentation. These results suggest that RA interferes with the apoptotic process at some point after its initiation stage. It has been suggested that negative selection involves not only TCR/CD3-mediated signals but also LFA-1-mediated signals. RA at 0.01 to 1 microM significantly inhibited the induction of thymocyte apoptosis by co-immobilized mAb to CD3 and LFA-1 molecules. RA by itself hardly induced apoptosis, but enhanced glucocorticoid-induced apoptosis. The results suggest that thymic selection might be influenced by RA at near-physiologic concentrations. The receptors of glucocorticoids and RA belong to the erbA oncogene-related steroid hormone receptor superfamily. Thyroid hormones and 1 alpha,25-dihydroxy vitamin D3, whose receptors also belong to the superfamily, failed to modulate apoptosis in both T cell hybridomas and thymocytes.
通过TCR/CD3复合体刺激后，未成熟胸腺细胞和T细胞杂交瘤会发生凋亡。这种现象似乎与胸腺中T细胞克隆的阴性选择有关。在T细胞杂交瘤中，已表明糖皮质激素可抑制TCR/CD3介导的凋亡，而单独使用糖皮质激素则可诱导凋亡。0.1至10微摩尔的全反式维甲酸（RA）也可通过DNA片段化和细胞溶解评估抑制TCR/CD3介导的凋亡，但单独的RA几乎不诱导凋亡。RA增强了糖皮质激素诱导凋亡和抑制TCR/CD3介导凋亡的作用。离子霉素（一种钙离子载体）和佛波醇酯（蛋白激酶C的激活剂）的组合可模拟TCR/CD3介导的刺激，且RA也可抑制该组合诱导的DNA片段化。然而，RA未能抑制该组合诱导的细胞内Ca2+浓度升高或该组合诱导的蛋白激酶C从胞质部分向颗粒部分的转位。向培养物中添加RA的时间进程研究表明，添加RA延迟3至6小时并不会降低其对抗CD3诱导的DNA片段化的抑制作用。这些结果表明，RA在凋亡起始阶段后的某个时间点干扰凋亡过程。有人提出阴性选择不仅涉及TCR/CD3介导的信号，还涉及LFA-1介导的信号。0.01至1微摩尔的RA可显著抑制共固定化的抗CD3和LFA-1单克隆抗体诱导的胸腺细胞凋亡。RA本身几乎不诱导凋亡，但可增强糖皮质激素诱导的凋亡。结果表明，接近生理浓度的RA可能会影响胸腺选择。糖皮质激素和RA的受体属于erbA癌基因相关的类固醇激素受体超家族。甲状腺激素和1α,25-二羟基维生素D3，其受体也属于该超家族，未能调节T细胞杂交瘤和胸腺细胞中的凋亡。
