A Study on the Cytokine Messenger RNA Expression in Bronchial Mucosal Biopsies from Patients with Asthma

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To determine whether IL-5 is locally produced in the bronchial mucosa of asthmatics, and to ascertain the precise cell type producing this cytokine, we examined bronchial biopsies by non-radioactive in situ hybridization and immunohistochemistry. IL-5 cDNA probes were labeled with digoxigenin-dUTP and hybridized to frozen tissue sections. Hybridization signals were visualized by an immunohistochemistry technique. An IL-5-producing T cell clone derived from a patient with adult T cell leukemia was used as a positive control. Specific hybridization signals for IL-5 mRNA were observed in six of the eight biopsy specimens from asthmatics. No hybridization signal was detected in the control subject in whom no underlying disease was found. Immunohistochemistry staining of serial sections using a panel of monoclonal antibodies against lymphocyte subsets strongly suggested that cells expressing mRNA for IL-5 were T cells. These results suggested that a cell-cell inteaction between T cells and eosinohils through IL-5 may play an important role in the airway inflammation in asthma.When stimulated with mite antigens, peripheral blood mononuclear cells (PBMC) obtained from mite-sensitive asthmatics, release eosinophil chemotactic factor(s)(ECF), a type of protein. To characterlize this factor, cDNA libraries were formulated from both PBMC stimulated with mite antigens and those not stimulated with mite antigens, then underwent subtraction and differential screening. We obtained 13 genes whose expression had increased due to mite antigens. Of these, nine were mitochondrial genes, two, h-satellite DNA III,one, factor XIII,and one, ferritin heavy subunit. Gene(s) which might be related to eosinophil chemotactic activity were not obtained in the present experiments. However, as a result of polymerase chain reaction on both cDNA libraries, IL-5 genes were amplified only from the cDNA library which had been stimulated with mite antigens.