Aspergillosis and lung defenses.

Aspergillosis refers to any of the illnesses caused by fungi that are members of the genus Aspergillus. The diseases range from allergic responses that occur in the absence of fungal growth (asthma, hypersensitivity pneumonitis), to colonization with or without an allergic component (allergic bronchopulmonary aspergillosis, aspergilloma, saprophytic involvement of infarcted tissue), to invasion and destruction of lung parenchyma (invasive aspergillosis, chronic necrotizing pulmonary aspergillosis). The development of lung infection and/or disease depends on interaction among three factors: the characteristics of the fungus (virulence factors), the status of host defense mechanisms, and the type of exposure. The purpose of this article is to review these factors and their relationship to the clinical syndromes of aspergillosis.