The activation of caspase-3 and DNA fragmentation in B cells phagocytosed by macrophages.
Apoptotic signaling of mammalian cells involves two pathways: the death receptor and mitochondrial pathways. In this in vivo study, we investigated apoptotic signaling of B cells in mouse germinal centers (GCs) of gut-associated lymphoid tissues (GALTs) using transmission electron microscopy (TEM), terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick-end labeling (TUNEL), immunofluorescence of members of caspase family and cFLIP(L), and caspase activity assay. It was very difficult to ultrastructurally differentiate B cells undergoing apoptosis from B cells differentiating into memory cells or plasma cells among B cells constituting GCs. Isolated B cells in GCs showed no active form of caspase-3 or TUNEL immunoreactivity, but expressed cFLIP(L). Contrary to isolated B cells, apoptotic B cells phagocytosed by macrophages exhibited immunoreactivity of the active form of caspase-3 and TUNEL, but lacked the cFLIP(L) expression. The caspase activity assay in GALTs clearly showed intense activity of caspase-3, caspase-9, and caspace-8 that was high in order. Therefore, the death receptor pathway accompanying the increased activity of caspase-3 and caspase-8 may be blocked by the expression of cFLIP(L) in B cells of GALTs. Moreover, both the activation of caspase-3 and DNA fragmentation first occur only when B cells are phagocytosed by macrophages.
Ninomiya
Eiji
E
Department of Anatomy and Biology, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki, Osaka 569-8686, Japan.
Ito
Yuko
Y
Shibata
Masa-Aki
MA
Kawashima
Keisei
K
Sakamoto
Takeshi
T
Maruyama
Eikun
E
Doi
Hisao
H
Tokitsu
Kosuke
K
Otsuki
Yoshinori
Y
D000818:Animals; D017209:Apoptosis; D001402:B-Lymphocytes / Q000166:cytology* / Q000378:metabolism*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D053938:DNA Fragmentation; D004789:Enzyme Activation; D005260:Female; D018858:Germinal Center / Q000166:cytology / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D047908:Intracellular Signaling Peptides and Proteins; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D008854:Microscopy, Electron; D010587:Phagocytosis; D015398:Signal Transduction
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins; C506387:Cflar protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; C505409:Casp3 protein, mouse; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases