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