GM-CSF, IL-5 and RANTES immunoreactivity and mRNA expression in chronic hyperplastic sinusitis with nasal polyposis (NP)

Background Eosinophils are a prominent feature of chronic hyperplastic sinusitis with nasal polyposis (CHS/NP). Our previous studies showed that their presence was associated with the expression of GM‐CSF and RANTES mRNA. In allergic NP, increased expression of IL‐5 was also found. Objective We wished to examine cytokine immunoreactivity for IL‐5, GM‐CSF and RANTES mRNA in allergic and non‐allergic NP and compare immunoreactivity with expression of cytokine mRNA by in situ hybridization. Methods NP were obtained from five allergic and eight non‐allergic subjects with CHS/NP. Middle turbinate tissue from eight normal subjects were used as controls. Cell‐associated cytokine mRNA was detected by in situ hybridization (ISH). Cytokine immunoreactive cells were enumerated by immunostaining. Colocalization immunostaining was also performed to identify specific cell types producing IL‐5. Results Immunostaining for GM‐CSF, IL‐5 and RANTES protein was increased in both allergic and non‐allergic NP compared with control middle turbinates. Allergic polyps contained greater numbers of IL‐5 immunoreactive cells (P = 0.01), whereas non‐allergic polyps contained greater numbers of GM‐CSF immunoreactive cells (P = 0.04). Immunostaining was primarily associated with inflammatory cells, but immunostaining for RANTES and, to a lesser extent GM‐CSF, was also seen in the epithelium. The density of immunoreactive cells was variably correlated with cytokine mRNA+ cells (GM‐CSF: R = 0.56, P = 0.05; IL‐5: R = 0.76, P = 0.003; and RANTES: R = 0.89, P = 0.0005). Colocalization immunostaining revealed that the majority of IL‐5 immunoreactive cells in both allergic and non‐allergic NP were T lymphocytes. However, allergic NP contained greater numbers of IL‐5+/CD3+ T lymphocytes and IL‐5+ mast cells, whereas non‐allergic NP contained greater numbers of IL‐5+ eosinophils. Conclusion We conclude that GM‐CSF, IL‐5 and RANTES are produced in increased amounts in both allergic and non‐allergic NP. Distinguishing features of non‐allergic NP include fewer numbers of CD3 T lymphocytes, fewer IL‐5+/CD3+ T lymphocytes and greater numbers of IL‐5+ eosinophils. These differences may suggest different mechanisms of eosinophil accumulation and activation in allergic vs non‐allergic NP.