A component of airborne fungi directly activates a specific type of immune cell in the lung, promoting allergic airway disease, reports a study published this week in Nature Medicine. This finding clarifies how environmental triggers can induce lung disease.
Spores from airborne fungi are commonly found both indoors and outdoors and are regularly inhaled. Once inhaled, the fungi are cleared by the immune system in the lung; however, some individuals develop an allergic response to the fungi that is associated with severe asthma and decreased lung function.
Dale T. Umetsu and colleagues confirm that inhalation of the common fungus Aspergillus fumigatus induces allergic lung disease in mice. This response is dependent on a specific type of immune cell in the lung, the invariant natural killer T (iNKT) cell, as exposure to fungi does not impair lung function in mice deficient in iNKT cells. These cells recognize asperamide B, a lipid molecule purified from the fungi. This lipid alone can directly bind to and activate mouse and human iNKT cells, thus eliciting an inflammatory immune response and impaired lung function in mice.