Grebe Kristie M, Clarke Raedun L, Potter Terry A
Integtrated Department of Immunology, National Jewish Medical and Research Center and University of Colorado Health Science Center, Denver, CO 80206, USA.
Proc Natl Acad Sci U S A. 2004 Jul 13;101(28):10410-5. doi: 10.1073/pnas.0402079101. Epub 2004 Jul 1.
Thymocytes that are not positively selected are said to undergo "death by neglect." We have found that ligation of CD8, either by antibodies or MHC class I molecules, induces apoptosis of CD4(+)CD8+ double-positive (DP) thymocytes. The susceptibility of thymocytes to CD8-mediated apoptosis is developmentally regulated and confined to a subpopulation of DP thymocytes. Stimulation through CD3 protects thymocytes from CD8-mediated apoptosis. We suggest that during thymocyte development, binding of CD8 to MHC class I molecules without T cell receptor engagement induces apoptosis in immature DP thymocytes. Our data are consistent with a model in which thymocytes that do not survive positive selection undergo "death by instruction" instead of death by neglect.
未被阳性选择的胸腺细胞被认为会经历“被忽视的死亡”。我们发现,通过抗体或MHC I类分子连接CD8会诱导CD4(+)CD8+双阳性(DP)胸腺细胞凋亡。胸腺细胞对CD8介导的凋亡的敏感性受到发育调控,且局限于DP胸腺细胞的一个亚群。通过CD3刺激可保护胸腺细胞免受CD8介导的凋亡。我们认为,在胸腺细胞发育过程中,CD8与MHC I类分子结合而无T细胞受体参与会诱导未成熟DP胸腺细胞凋亡。我们的数据与一个模型相符,即未通过阳性选择存活下来的胸腺细胞会经历“指令性死亡”而非被忽视的死亡。