Local complement activation in nasal polyposis.

Objectives/hypothesis: The role of the complement system in nasal polyps (CRSwNP) has so far scarcely been studied. Because nasal polyps are characterized by bacterial colonization, and the complement system is an effective defense mechanism, it might be involved in the pathogenesis of CRSwNP. This study was designed to investigate the local and systemic activation of the complement system in CRSwNP versus control mucosa in relation to the local and systemic eosinophilic and neutrophilic inflammation and local plasma exudation.

Methods: Concentrations of complement factors C3a desArg and C5a desArg, and of albumin, alpha2-macroglobulin, eosinophilic cationic protein, and myeloperoxidase were determined on nasal secretions and serum from 12 CRSwNP patients and 10 control patients. Tissue cryosections were stained for the membrane attack complex (C5b9)

Results: We found a significantly higher concentration of C3a desArg and C5a desArg in nasal secretions from CRSwNP patients compared to controls, whereas the serum levels between the two groups did not differ significantly. Significant correlations were found between C5a desArg and eosinophil cationic protein in nasal secretions. Staining for the membrane attack complex revealed a deposition around blood vessels and the basal membrane exclusively in nasal polyp tissue.

Conclusions: These data support the hypothesis that, in addition to the adaptive immune responses, the complement system is involved in the pathogenesis of CRSwNP and may contribute to typical features such as edema and granulocytic inflammation.