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Triggering HLA-DR molecules on human peripheral monocytes induces their death
A Thibeault1, H Zekki, W Mourad
1Centre de recherche en Rhumatologie et Immunologie, CHUQ, Pavillon CHUL, Université Laval, Quebec, Canada.
Cellular Immunology
|March 6, 1999
Summary
Ligation of MHC class II molecules on monocytes triggers apoptosis, a novel cell death pathway. This process is modulated by cell interactions and inflammatory signals, impacting inflammatory responses and monocyte homeostasis.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- The role of MHC class II molecules in human monocyte function is well-established, but their involvement in monocyte death pathways remains unclear.
- Understanding monocyte death mechanisms is crucial for regulating inflammatory processes and maintaining immune homeostasis.
Purpose of the Study:
- To investigate the potential role of MHC class II engagement in inducing human monocyte death.
- To characterize the mechanisms and regulatory factors involved in MHC class II-mediated monocyte apoptosis.
Main Methods:
- Primary human monocytes were stimulated to ligate MHC class II molecules.
- Apoptosis was assessed using standard assays, and involvement of specific signaling pathways (Fas, TNF-alpha, CD40) and cell-cell interactions (CD18) was investigated.
- Monocyte priming with IFN-gamma and LPS treatment were used to modulate the death process.
Main Results:
- Ligation of MHC class II (specifically HLA-DR) on primary monocytes induces rapid apoptosis.
- This cell death is independent of de novo protein synthesis, Fas, and TNF-alpha pathways, and is not rescued by CD40 ligation.
- Cell-cell interactions involving beta2-integrin CD18 are critical for this apoptotic execution.
- IFN-gamma priming enhances HLA-DR-mediated monocyte death, while LPS treatment reverses it.
Conclusions:
- MHC class II molecules, particularly HLA-DR, act as potent mediators of monocyte apoptosis.
- This novel pathway of monocyte death plays a significant role in controlling inflammatory outcomes and regulating monocyte hemostasis.