CD14-dependent clearance of apoptotic cells: relevance to the immune system.

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.