Related Experiment Video
Updated: Oct 17, 2026

Experimental Analysis of Apoptotic Thymocyte Engulfment by Macrophages
Published on: May 24, 2019
An auxiliary mode of apoptotic DNA fragmentation provided by phagocytes
D McIlroy1, M Tanaka, H Sakahira
1Department of Genetics, Japan Science and Technology Corporation, Suita, Osaka 565-0871, Japan.
Abstract:
CAD (caspase-activated DNase) can cause DNA fragmentation in apoptotic cells. Transgenic mice that ubiquitously express a caspase-resistant form of the CAD inhibitor (ICAD) were generated. Thymocytes prepared from the mice were resistant to DNA fragmentation induced by a variety of stimuli. However, similar numbers of TUNEL-positive cells were present in adult tissues of transgenic and wild-type mice. Exposure to gamma-irradiation caused a striking increase in the number of TUNEL-positive cells in the thymus of wild-type, but not transgenic, mice. TUNEL-positive nuclei in transgenic mice were confined to thymic macrophages. When apoptotic thymocytes from the transgenic mice were cocultured with macrophages, the thymocytes underwent phagocytosis and their chromosomal DNA underwent fragmentation. This DNA fragmentation was sensitive to inhibitors that block the acidification of lysosomes. Hence, we conclude that the DNA fragmentation that occurs during apoptosis not only can result cell-autonomously from CAD activity but can also be attributed to a lysosomal acid DNase(s), most likely DNase II, after the apoptotic cells are engulfed.
Related Concept Videos
Phagocytosis of Apoptotic Cells
Normal cells contain receptors that prevent them from being recognized by phagocytes.
Apoptosis
The Extrinsic Apoptotic Pathway
The Intrinsic Apoptotic Pathway
Autophagic Cell Death
Autophagy and Apoptosis
Autophagy can activate apoptosis. In normal conditions, the autophagy activating protein Beclin-1 and pro-apoptotic...
Immune Surveillance by NK Cells and Phagocytes
Natural Killer Cells: The Fast Responders
NK cells are large granular lymphocytes found in the blood and lymphatic system. These...

