Exposure, sensitization, and mechanisms of fungus-induced asthma

Abstract

Healthy individuals are continuously exposed to fungal biomass, which includes live and dead spores and fungal debris that is entrapped in the airways. In patients with asthma and/or atopy, exposure to fungal biomass might result in age-dependent sensitization and asthmatic reactions. Interaction with Toll-like receptors (TLRs) of the innate immune defense (alveolar macrophages and epithelial cells) and protease-activated receptors (PARs) determine the effectiveness of elimination of fungal material. The association of sensitization to Alternaria with severe asthma is discussed in relation to the age-dependent sensitization, rate of release of allergens from spores, and activity of its proteases. A model is described concerning the influence of polymorphic genes for airway hyperresponsiveness (AHR) and atopy, showing a cumulating influence on susceptibility for allergen-induced asthma, and explaining that fungus-induced airway obstruction is mainly associated with more severe asthma.