Asthma is characterized by variable airflow
obstruction, airway hyperresponsiveness, and airway
inflammation. Mast cells have long been thought to play a central role in
asthma through their ability to release proinflammatory mediators, but this role has been questioned by the lack of efficacy of
antihistamines and so-called mast cell-stabilizing drugs. Recent comparisons between the immunopathology of
asthma and eosinophilic
bronchitis have led to the re-emergence of the mast cell as a pivotal cell in
asthma. Eosinophilic
bronchitis is a condition in which patients present with
chronic cough, and shares many of the inflammatory features associated with
asthma, but without variable airflow obstruction or
airway hyperresponsiveness. The only striking pathologic difference between these conditions is that, in
asthma, the airway smooth muscle is infiltrated by mast cells. This suggests that interactions between mast cells and airway smooth muscle cells are critical for the development of the disordered airway physiology in
asthma.