Bioaerosols and innate immune responses in airway diseases

Purpose of review We review the role of bioaerosols in the pathogenesis of inflammatory airway disease. The focus is on recent discoveries in innate immune responses induced by common components of bioaerosols. Recent findings Common components of bioaerosols include endotoxin, peptidoglycan and beta-glucan; all of which have been associated with inflammatory airway disease. Endotoxin signaling through toll-like receptor 4 is well characterized and updated. Peptidoglycan is now known to signal through three types of molecules: toll-like receptor 2; peptidoglycan recognition proteins; and nucleotide-binding oligomerization domain molecules. Beta-glucan, a common fungal cell wall component, signals through the newly discovered receptor, dectin-1. Emerging data indicate that genetic polymorphisms influence the response to bioaerosols. Summary Activation of the innate immune system by bioaerosols is becoming better understood. This knowledge provides an opportunity to better prevent and treat airway diseases that result from environmental exposure.