Foreword

Like the gut, the lung resides in a relatively unique, outside-in position, in that it sits squarely within the body while interacting directly with the outside world. The lung’s interaction with ambient air is so extensive that it includes a surface area approaching that of a tennis court. While this tremendous surface area is required for the lung to perform its essential gas-exchange functions, it is also inherently problematic. Because like the tennis court, the lung is literally bombarded daily by thousands of inorganic, organic and microbial intruders, that all harbour “ill-will” to one extent or another. So like the Kenny Roger’s song, “The Gambler”, where accurately reading the eyes of one’s opponent is vital, the lung needs to carefully balance its response to each challenge in order to maximize benefit and limit harm.

Much of the lung’s initial reaction to injury has been thought to depend on the sentinel function of the alveolar macrophage, the “decider” so to speak; the cell that chooses whether a challenge warrants a response and how vigorous that response might be. While this concept of the alveolar macrophage has its merits, it is also limited. It is now understood that the functions regulated by the alveolar macrophage are much more extensive and nuanced than were once conjectured. As is beautifully presented within these pages, the alveolar macrophage not only holds a key position as the first responder to insults, it also performs crucial functions in the maintenance of lung structure, cancer biology and many more. This strategically places the alveolar macrophage at a regulatory checkpoint, critical for the maintenance of homeostasis, ripe for dysregulation to the point of causing disease, and essential to understand for the development of novel therapeutic approaches for acute and chronic disease.