Phenotype of cells positive for interleukin-4 and interleukin-5 mRNA in allergic tissue reactions.

We have investigated the phenotype of cells positive for IL-4 and IL-5 mRNA in the nasal mucosa of subjects with allergic rhinitis and in bronchoalveolar lavage and bronchial biopsies from atopic asthmatic subjects. The method employed was immunochemistry followed by in situ hybridization using either 35S- or digoxigenin-labelled riboprobes. With nasal and bronchial tissue, this double ICC/ISH method revealed that more than 70% of IL-4 and IL-5 mRNA+ cells were T cells. The remaining IL-4 and IL-5 signals were co-localized to tryptase-positive mast cells and EG2+ eosinophils. Occasional IL-4 and IL-5 mRNA cells were observed in non-asthmatic control subjects, the large majority being CD3+ cells. These results indicate that CD3+ cells are the principal cellular source of IL-4 and IL-5 transcripts in atopic asthma and allergic rhinitis.