H. pylori receptor MHC class II contributes to the dynamic gastric epithelial apoptotic response.
OBJECTIVE
To investigate the role of MHC class II in the modulation of gastric epithelial cell apoptosis induced by H pylori infection.


METHODS
After stimulating a human gastric epithelial cell line with bacteria or agonist antibodies specific for MHC class II and CD95, the quantitation of apoptotic and anti-apoptotic events, including caspase activation, BCL-2 activation, and FADD recruitment, was performed with a fluorometric assay, a cytometric bead array, and confocal microscopy, respectively.


RESULTS
Pretreatment of N87 cells with the anti-MHC class II IgM antibody RFD1 resulted in a reduction in global caspase activation at 24 h of H pylori infection. When caspase 3 activation was specifically measured, crosslinking of MHC class II resulted in a marked reduced caspase activation, while simple ligation of MHC class II did not. Crosslinking of MHC class II also resulted in an increased activation of the anti-apoptosis molecule BCL-2 compared to simple ligation. Confocal microscope analysis demonstrated that the pretreatment of gastric epithelial cells with a crosslinking anti-MHC class II IgM blocked the recruitment of FADD to the cell surface.


CONCLUSIONS
The results presented here demonstrate that the ability of MHC class II to modulate gastric epithelial apoptosis is at least partially dependent on its crosslinking. Furthermore, while previous research has demonstrated that MHC class II signaling can be pro-apoptotic during extended ligation, we have shown that the crosslinking of this molecule has anti-apoptotic effects during the earlier time points of H pylori infection. This effect is possibly mediated by the ability of MHC class II to modulate the activation of the pro-apoptotic receptor Fas by blocking the recruitment of the accessory molecule FADD, and this delay in apoptosis induction could allow for prolonged cytokine secretion by H pylori-infected gastric epithelial cells.
Bland
David A
DA
Children's Hospital, Room 2.300, University of Texas Medical Branch, 301 University Blvd. Galveston, TX 77555, USA.
Suarez
Giovanni
G
Beswick
Ellen J
EJ
Sierra
Johanna C
JC
Reyes
Victor E
VE
D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D053938:DNA Fragmentation; D004789:Enzyme Activation; D004848:Epithelium / Q000378:metabolism* / Q000382:microbiology*; D005753:Gastric Mucosa / Q000378:metabolism* / Q000382:microbiology*; D005802:Genes, MHC Class II; D016481:Helicobacter Infections / Q000378:metabolism*; D016480:Helicobacter pylori / Q000378:metabolism*; D000949:Histocompatibility Antigens Class II / Q000378:metabolism*; D006801:Humans; D018613:Microscopy, Confocal; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D019014:fas Receptor / Q000096:biosynthesis
D000949:Histocompatibility Antigens Class II; D019253:Proto-Oncogene Proteins c-bcl-2; D019014:fas Receptor; D053148:Caspase 3; D020169:Caspases