McConkey D J, Hartzell P, Amador-Pérez J F, Orrenius S, Jondal M
Department of Toxicology, Karolinska Institute, Stockholm, Sweden.
J Immunol. 1989 Sep 15;143(6):1801-6.
Development of tolerance to self Ag occurs during a negative cell selection process in the thymus. This selection process is thought to involve interactions between Ag-specific thymocyte receptors and self Ag presented by the MHC proteins on accessory cells, resulting in deletion of potentially harmful self-reactive precursors. However, the mechanisms underlying this clonal deletion have not been identified. In confirmation of previous findings (C. A. Smith, G. T. Williams, R. Kingston, E. J. Jenkins, and J. J. T. Owen, 1989. Antibodies to CD3/T-cell receptor complex induce death by apoptosis in immature T cells in thymic cultures. Nature 337:181), we have found that an anti-CD3 antibody stimulated DNA fragmentation, characteristic of a suicide mechanism known as apoptosis or programmed cell death (PCD), in suspensions of human thymocytes. Endonuclease activation and cell killing were dependent on an early, sustained increase in cytosolic Ca2+ concentration, most of which was of extracellular origin. Although the magnitude and duration of the Ca2+ increase were similar to those observed in response to Con A, the mitogen did not stimulate DNA fragmentation or cell death. Phorbol ester prevented Ca2+-dependent DNA fragmentation and cell killing in response to anti-CD3 or other agents that stimulated PCD, suggesting that activation of protein kinase C abrogated cell suicide. Disappearance of CD4+CD8+ immature thymocytes was generally observed in response to all agents that stimulated PCD, whereas mature PBL were insensitive to stimulation of PCD. Our results suggest that antibody-mediated stimulation of immature thymocytes via the TCR complex results in Ca2+-dependent, endonuclease-mediated cell killing, depending on the activation status of protein kinase C.
对自身抗原的耐受性在胸腺中的阴性细胞选择过程中形成。据认为，这种选择过程涉及抗原特异性胸腺细胞受体与辅助细胞上由MHC蛋白呈递的自身抗原之间的相互作用，从而导致潜在有害的自身反应性前体细胞的清除。然而，这种克隆清除的潜在机制尚未明确。为证实先前的研究结果（C. A. 史密斯、G. T. 威廉姆斯、R. 金斯顿、E. J. 詹金斯和J. J. T. 欧文，1989年。抗CD3/T细胞受体复合物抗体在胸腺培养物中诱导未成熟T细胞凋亡死亡。《自然》337:181），我们发现抗CD3抗体可刺激人胸腺细胞悬液中的DNA片段化，这是一种名为凋亡或程序性细胞死亡（PCD）的自杀机制的特征。核酸内切酶激活和细胞杀伤依赖于胞质Ca2+浓度的早期持续升高，其中大部分Ca2+来源于细胞外。尽管Ca2+升高的幅度和持续时间与对伴刀豆球蛋白A反应时观察到的相似，但该促有丝分裂原并未刺激DNA片段化或细胞死亡。佛波酯可阻止因抗CD3或其他刺激PCD的试剂而引起的Ca2+依赖性DNA片段化和细胞杀伤，这表明蛋白激酶C的激活可消除细胞自杀。通常观察到，所有刺激PCD的试剂都会导致CD4+CD8+未成熟胸腺细胞消失，而成熟外周血淋巴细胞对PCD刺激不敏感。我们的结果表明，抗体通过TCR复合物介导的未成熟胸腺细胞刺激会导致Ca2+依赖性、核酸内切酶介导的细胞杀伤，这取决于蛋白激酶C的激活状态。
