Mechanisms of pyknotic cell death in vivo and their biological significance

在发育过程中，大多数细胞程序性死亡被认为是伴随DNA断裂的细胞凋亡。我们精确地检查了生发中心的胸腺细胞死亡和B细胞死亡，即原位“细胞死亡”，发现它们是固缩，核浓缩严重，没有DNA断裂；它们与典型的细胞凋亡完全不同，后者的特征是DNA断裂和边缘染色质凝聚。我们重新评估了各种细胞在体内的死亡，并在新的观点的基础上对原位细胞死亡进行了重新分类，以分析新型细胞死亡-固缩的机制，并描述其生物学意义。我们从形态学上分析了发育过程中体内细胞死亡，特别是指间组织中观察到的细胞死亡，发现该组织中的细胞死亡不伴随DNA断裂，因此我们得出结论，它们不是细胞凋亡。抗cd3抗体治疗引发的大量细胞死亡已经被发现是典型的细胞凋亡，因为它们在更早的阶段就分裂了DNA，可以观察到形态变化。我们已经承担了一个项目，开发一种单克隆抗体来检测pyknosis的最早迹象，pyknosis是一种垂死胸腺细胞的表面抗原，被巨噬细胞识别并摄入。这个项目一直在进行中，并将继续进行，直到抗原的开发。

Most of programmed cell deaths during the developmental processes have been considered to be apoptosis accompanying DNA fragmentation. We have precisely examined thymocyte deaths and B cell deaths in the germinal centers, i.e., "cell deaths" in situ, and found that they are pyknosis with heavy nuclear condensation without DNA fragmentation ; they are totally distinct from typical apoptosis, which is characterized by DNA fragmentation and marginal chromatin condensation. We re-evaluated various cell deaths in vivo, and rectategorize those in situ cell deaths on the basis of the novel point of view, in order to analyze the mechanisms of the new type of cell deaths, pyknosis, and to delineate their biological significance.We analyzed morphologically cell deaths in vivo during the development, especially the cell deaths observed in the interdigital tissues and found that the cell deaths in this tissue did not accompany DNA fragmentation, and accordingly, we concluded that they are not apoptosis. Massive cell deaths triggered by anti-CD3 antibody treatment have been found typical apoptosis, because they fragmented DNA at much earlier stages when morphological changes could be observed.We have undertaken a project to develop a monoclonal antibody to detect the earliest sign of pyknosis, a surface antigen of dying thymocytes to be recognized by macrophages for ingestion. This project has been underway, and will be pursued until the development of the antigen.