The role of airway macrophages in apoptotic cell clearance following acute and chronic lung inflammation

Grabiec, Aleksander M.; Hussell, Tracy

Since the initial discovery of defects in apoptotic cell clearance in asthma and COPD, great progress has been made in our understanding of the molecular mechanisms of efferocytosis and several new processes through which efferocytosis modulates host immune responses have been characterised (Fig. 1) . Consequently, new questions have emerged regarding the role of apoptotic cell removal in lung homeostasis and the most important of them are listed in Box 1. Future studies addressing these questions, especially attempts to therapeutically manipulate efferocytosis in the clinic, should be designed in the context of the multiple roles of apoptotic cell phagocytosis in resolution of inflammation and microbial infections. Box 1. Future questions in apoptotic cell removal in the airspaces • Does efferocytosis polarise airway macrophages to an M2 phenotype or are M2 polarised airway macrophages better at efferocytosis? • What is the impact of the tissue microenvironment on apoptotic cell recognition receptor repertoires and outcome of their ligation? • Is homeostatic apoptotic cell clearance different in requirements and consequences to clearance of cells during inflammation? • What is the impact of the altered lung environment in asthma, COPD and CF on apoptotic cell clearance? Open Access This article is distributed under the terms of the Creative Comm ons Attribution 4.0 International License (http:// creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.