TRAIL (Apo2 ligand) and TWEAK (Apo3 ligand) mediate CD4+ T cell killing of antigen-presenting macrophages.
The human marrow produces approximately 1010 monocytes daily, and this production must be balanced by a similar rate of destruction. Monocytes/macrophages can undergo apoptosis after activating CD4+ T cells, suggesting one mechanism that may contribute to macrophage homeostasis. Previous reports indicate that Fas-Fas ligand interactions are the principle molecules mediating this response. However, D10, an Iak-restricted cloned Th2 line, will similarly induce apoptosis in Ag-presenting macrophages, and D10 cells lack Fas ligand. To confirm that D10 cells kill macrophages through Fas-independent pathways, D10 cells were shown to kill MRL lpr/lpr (Iak) macrophages in an Ag-dependent fashion, indicating additional mechanisms. Recent reports demonstrate that TNF-related apoptosis-inducing ligand (TRAIL), interacting with Apo2, and TNF-like weak inducer of apoptosis (TWEAK), interacting with Apo3, will induce apoptosis in some cells. Using Abs to TRAIL and an Apo3-IgG Fc fusion protein, we demonstrated that D10 cells express both TRAIL and TWEAK. The Apo3 fusion protein, but not human IgG, inhibited D10-induced macrophage apoptosis, as did anti-TRAIL. Further studies demonstrated that AE7, a cloned Th1 line, and splenic T cells express TWEAK, TRAIL, and Fas ligand, and inhibiting these molecules also inhibited macrophage killing. These results indicate that D10 cells induce macrophage apoptosis through TRAIL- and TWEAK-dependent pathways. Because normal T cells also express these molecules, these results support the concept that T cells have multiple pathways by which to induce macrophage apoptosis. These pathways may be important in immune processes such as macrophage homeostasis as well as in down-regulation of immune responses and elimination of macrophages infected with intracellular organisms.
Kaplan
M J
MJ
Department of Medicine, University of Michigan, and Veterans Affairs Medical Center, Ann Arbor MI 48109, USA.
Ray
D
D
Mo
R R
RR
Yung
R L
RL
Richardson
B C
BC
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D017209:Apoptosis / Q000276:immunology*; D051017:Apoptosis Regulatory Proteins; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002352:Carrier Proteins / Q000096:biosynthesis / Q000502:physiology*; D002460:Cell Line; D002478:Cells, Cultured; D000074049:Cytokine TWEAK; D003602:Cytotoxicity, Immunologic / Q000276:immunology*; D053222:Fas Ligand Protein; D005260:Female; D008024:Ligands; D017737:Macrophages, Peritoneal / Q000276:immunology* / Q000378:metabolism / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000502:physiology*; D051379:Mice; D008805:Mice, Inbred A; D008806:Mice, Inbred AKR; D008810:Mice, Inbred C57BL; D019463:Mice, Inbred MRL lpr; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000502:physiology*; D048069:Tumor Necrosis Factors; D019014:fas Receptor / Q000378:metabolism / Q000502:physiology
D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D000074049:Cytokine TWEAK; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008024:Ligands; D008562:Membrane Glycoproteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; C505654:Tnfsf10 protein, mouse; C491645:Tnfsf12 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D048069:Tumor Necrosis Factors; D019014:fas Receptor