The alveolar macrophages in asthma: a double-edged sword

Asthma is a complex disease of the lungs, which is characterized by airway inflammation and airway hyperresponsiveness (AHR). Alveolar macrophages (AMs), one of the prominent immune system cells found in the airways, have been implicated in the development and progression of asthma. AMs constitute a unique subset of pulmonary macrophages, which serve as a first line of defense against foreign invaders to the lung tissue. In addition, based on human and animal studies, they have also been found to regulate pro- and anti-inflammatory responses in the airways, suggesting that these cells have a critical role in asthma. In this review, our focus is to evaluate the relevance of AMs in the context of asthma, and the underlying mechanisms that regulate their functions.