Quantitative investigations of apoptosis of murine mononuclear phagocytes during mild hyperthermia.
DNA fragmentation in murine monocytes and freshly harvested resident peritoneal macrophages (RPM) was assessed. Similar proportions of fragmented DNA were present in both cell types indicating that apoptosis is a significant occurrence in these cells and may provide a mechanism for controlling the numbers of mononuclear phagocytes in the tissues that house them. Culturing both of these cell types at 41 degrees C for 5 hr revealed a significant increase in the proportion of fragmented DNA only in cultures containing RPM. These latter preparations when cytophotometrically assessed also displayed reduced Feulgen DNA and cytoplasmic naphthol yellow S staining, again confirming the presence of apoptosis. It is suggested that the induction of apoptosis by mild hyperthermia may therefore be due to the relative absence of a temperature-sensitive inhibitor of apoptosis in a significant proportion of resident peritoneal macrophages. Lastly, electron microscope assessment indicated that the apoptotic macrophages were engulfed by their nonaffected neighbors. Programmed cell death in macrophage populations followed by phagocytosis of the apoptotic cells may therefore be a mechanism for controlling macrophage numbers in mammalian organisms.
Papadimitriou
J M
JM
Department of Pathology, University of Western Australia, Nedlands.
van Bruggen
I
I
D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D004249:DNA Damage; D006358:Hot Temperature; D066298:In Vitro Techniques; D008264:Macrophages / Q000166:cytology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008854:Microscopy, Electron; D009000:Monocytes / Q000166:cytology*