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To study the expression of important elements of the innate immune responses in human sinonasal tissue to elucidate its potential role in mucosal inflammation. Design: We studied human sinonasal tissue from patients with chronic rhinosinusitis and an immortalized epithelial cell line to detect the expression of innate immune effectors and the responses of these cells to stimulation with compounds associated with pathogenic organisms. Patients: Nine individuals undergoing endoscopic sinus surgery for chronic rhinosinusitis. Main Outcome Measures: Expression of complement components and toll-like receptors. Results: We found detectable levels of messenger RNA for all toll-like receptors in human sinonasal tissue and in the BEAS-2B epithelial cell line. Expression of several components of the alternate pathway of complement (factors B, H, and I and properdin) was constitutively present in unstimulated BEAS-2B cells and was readily detectable in human sinonasal tissue. Stimulation of BEAS-2B cells with the toll-like receptor 3 ligand doublestranded RNA resulted in increased expression of messenger RNA for factors B and H but not for properdin or factor I. Conclusions: Toll-like receptors and the alternate pathway of complement are important components of innate immunity that are expressed in human sinonasal epithelium in vivo and in cultured airway epithelial cells in vitro. The expression of some of these components can be significantly induced by stimulation via toll-like receptors, and epithelial expression of components of innate immunity may play a role in inflammation in chronic rhinosinusitis.

Sepsis or septic shock is frequently associated with activation of the complement system, coagulation and fibrinolytic changes and the release of several cytokines. In this study we analyzed the relation of complement activation to the inflammatory mediators, hemodynamic and biochemical parameters and severity of illness and outcome in 20 consecutive patients with clinically defined sepsis. Levels of C3a and C3d were elevated in 90% of the patients (median levels 0.19 mg/l and 8.6 mg/l respectively) in comparison to 14% and 42%, respectively of 7 patients with non-septic shock. Levels of C4 were decreased in only 1 of the 20 septic patients. Levels of TNF and IL-6 were elevated in 94% and 100% of the patients, Levels of TNF and IL-6 were elevated in 94% and 100% of the patients, respectively (median levels 122 ng/l and 1300 U/ml) and were clearly interrelated (r = 0.67, p less than 0.01). C3a levels correlated with the APACHE II score (r = 0.57, p less than 0.05) and high C3a levels were associated with fatal outcome (p less than 0.05). C3a was also correlated inversely with mean arterial pressure (r = 0.50, p less than 0.01). Levels of complement C3a and C3d significantly correlated with levels of plasminogen activator inhibitor-1 (PAI) and correlated inversely with AT-III levels. We found no correlation between these complement products and leukocyte counts or lactate levels, nor was there a correlation between C3a or C3d and the cytokines TNF and IL-6. Levels of C3a and C3d did not decrease significantly during the first 24 h of treatment, in contrast to a clear decrease in IL-6 levels in all patients and a decrease in TNF in the surviving patients. TNF levels remained stable or increased in the non-survivors. We conclude that both the complement system and the cytokine system are involved in the pathogenesis of septic shock and may be involved in the development of some of the fatal complications like hypotension and disseminated intravascular coagulation.

The epithelium is thought to serve an important barrier function in the airways. However, growing evidence now supports the notion that the respiratory epithelium plays a key role in host responses to infectious and allergenic stimuli. The epithelium functions to produce a variety of proinflammatory cytokines during the inflammatory response. More recently, the epithelium has been shown to express a variety of receptors that can recognize microorganisms, such as toll-like receptors (TLRs), as well as complement and acute phase proteins. Additionally, the cell surface of epithelial cells have also been shown to express a variety of costimulatory molecules which may be involved in regulating the activation of antigen-specific T cells in the airways. This paper reviews the novel ways by which the epithelium may function in both the innate and adaptive immune responses of the airways.

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