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.