Enhanced soluble interleukin‐5 receptor alpha expression in nasal polyposis

Abstract

Background: Alternative splicing of the interleukin‐5 receptor alpha (IL‐5Rα)‐subunit leads to the generation of a signalling, membrane‐anchored (TM) isoform, or a secreted [soluble (SOL)], antagonistic variant. Given the key role of IL‐5 in eosinophil function, we investigated SOL IL‐5Rα expression pattern in an eosinophil‐associated disease such as nasal polyposis (NP). Methods: An SOL IL‐5Rα enzyme‐linked immunosorbent assay and quantitative real‐time polymerase chain reaction (PCR) were established and applied in serum, nasal secretion and nasal tissue of controls (n = 12), and NP patients (n = 42) with or without asthma. Results: Analysis of serum, nasal secretion, and nasal tissue samples revealed that SOL IL‐5Rα protein concentrations were significantly increased in NP vs control tissue. Within the NP group, there was a significant up‐regulation of SOL IL‐5Rα in patients with systemic airway disease. These findings were confirmed at the mRNA level, using an optimized real‐time reverse‐transcriptase PCR procedure. Conclusions: This report demonstrates SOL IL‐5Rα transcript and protein up‐regulation in NP. Soluble IL‐5Rα differentiates nasal polyps with or without concomitant asthma. As SOL IL‐5Rα is strongly up‐regulated for disease and has antagonistic properties in vitro, our studies shed new light on the mechanisms of specific immunomodulatory therapies, such as anti‐IL‐5.