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CD14-dependent clearance of apoptotic cells: relevance to the immune system
1D Floor, Institute of Cell Signalling and School of Biomedical Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, NG7 2UH, UK. chris.gregory@nottingham.ac.uk
Abstract:
Until very recently, the function of CD14 was thought to be limited to innate immune responses to bacterial and other microbial structures. It is now known that macrophage CD14 serves an additional unexpected function, namely as a receptor involved in the recognition and phagocytosis of cells undergoing apoptosis. In stark contrast to its role in eliciting pro-inflammatory responses following binding of microbial ligands, macrophage CD14 mediates clearance of apoptotic cells without inciting inflammation. Increasing interest in the profoundly important final stage of apoptosis - the engulfment process - together with significant advances in knowledge of the immunological consequences of apoptotic-cell clearance and of the means by which signal transduction may be achieved following CD14-ligand binding have begun to produce a clearer picture of the role of CD14 in the immune system.
Insights
CD14 (Cluster of Differentiation 14) is newly recognized for its role in clearing apoptotic cells. This function is distinct from its known role in innate immunity, as it resolves inflammation rather than inciting it.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Previously, Cluster of Differentiation 14 (CD14) was primarily understood for its role in innate immunity, recognizing microbial structures.
- Emerging research indicates CD14 has a dual function within the immune system.
- Apoptosis, or programmed cell death, requires efficient clearance mechanisms to prevent tissue damage and secondary inflammation.
Purpose of the Study:
- To elucidate the novel function of macrophage CD14 in the recognition and clearance of apoptotic cells.
- To investigate the immunomodulatory consequences of CD14-mediated efferocytosis (clearance of apoptotic cells).
- To understand the signaling pathways involved in CD14's interaction with apoptotic cells.
Main Methods:
- Utilized macrophage cell models.
- Employed ligand-binding assays to study CD14 interactions.
- Investigated cellular responses, including phagocytosis and cytokine production, following CD14 engagement.
Main Results:
- Macrophage CD14 acts as a receptor for recognizing cells undergoing apoptosis.
- CD14 mediates the phagocytosis of apoptotic cells without triggering pro-inflammatory responses.
- This contrasts with CD14's known pro-inflammatory role upon binding microbial ligands.
Conclusions:
- Macrophage CD14 plays a critical, previously unrecognized role in the resolution of inflammation through efferocytosis.
- CD14-mediated clearance of apoptotic cells represents a key anti-inflammatory mechanism in the immune system.
- Further research into CD14 signaling in efferocytosis holds promise for understanding immune homeostasis and developing new therapeutic strategies.