The Role of Innate Immunity and Aeroallergens in Chronic Rhinosinusitis

Allergy has been inferred to contribute to the pathophysiology of chronic rhinosinusitis (CRS) although this role is controversial and the mechanism is debated. Furthermore, the role of aeroallergens in CRS is poorly defined and has been postulated to contribute to CRS through direct penetration in the sinuses or downstream systemic consequences. Common aeroallergens implicated in chronic rhinosinusitis include air pollution/second hand smoke, dust mite and pollen [<citeref rid=»ref1»>1</citeref>,<citeref rid=»ref2»>2</citeref>,<citeref rid=»ref3»>3</citeref>]. One emerging potential mechanism whereby aeroallergens contribute to CRS is through sinonasal epithelial barrier disruption (fig. <figref rid=»fig01»>1</figref>). Characterization of cytokine disruption of sinonasal epithelial cell barrier has been described including interleukin (IL)-4 and IL-13, as well as aeroallergens such as house dust mite and cigarette smoke. Recent results have demonstrated severe barrier disruption in response to direct application of either particulate matter (PM) or house dust mite (HDM) to sinonasal epithelial cells. Sinonasal epithelial barrier disruption may contribute to CRS by enabling the perpetual and chronic exposure of inflammatory allergens and stimuli. The sinonasal epithelial barrier plays a significant role in innate immune host defense. Mechanisms of innate immune defense include pattern recognition receptors (PRRs), secreted endogenous antimicrobials and inflammatory cytokines that aid in repair mechanisms including IL-33. Here we discuss recent evidence implicating aeroallergens and dysregulated host innate immune responses in the development of CRS. <figure id=»fig01»><no>1</no><figcap>Fig. 1. Aeroallergens and inflammatory stimuli disrupt sinonasal epithelial barrier function. These agents act to destabilize the barrier through stimulating endocytosis and destruction of cell junction proteins via oxidative stress and MyD88-dependent mechanisms. Furthermore, aeroallergens and inflammatory stimuli induce secretion of IL-25, IL-33, and TSLP from sinonasal epithelial cells.</figcap><figbody filename=»F01» filetype=»JPG»>F01</figbody></figure>