Defective Clearance of Apoptotic Cells (Efferocytosis) in Chronic Lung Diseases

Repair of airway epithelial injury and resolution of inflammation are highly regulated processes. Inefficient clearance of apoptotic cells (efferocytosis) has the potential to cause an accumulation of apoptotic material and the subsequent development of secondary necrosis and perpetuation of chronic inflammation. Alveolar macrophages have the major role in effectively clearing excess apoptotic cells in the airway. Several studies have identified defective efferocytosis in the airways of subjects with chronic pulmonary diseases including chronic obstructive pulmonary disease (COPD), asthma, lung cancer and cystic fibrosis. These defects have been shown to at least partially relate to reduced levels of soluble mediators including mannose binding lectin (MBL) and collectins (surfactant proteins A and D), as well as dysregulated expression of various macrophage surface receptors and molecular pathways. These defects in macrophage function are potential targets for new therapeutic interventions for chronic lung diseases.

Keywords: Alveolar macrophage, apoptosis, phagocytosis, efferocytosis, chronic lung disease, COPD.