Interleukin-5 gene expression in nasal mucosa and changes in amount of interleukin-5 in nasal lavage fluid after antigen challenge.

Eosinophils and their products are known to cause hyperreactivity and swelling of the nasal mucosa in subjects with nasal allergy. Interleukin-5 (IL-5) not only induces differentiation and proliferation of immature eosinophils but also causes mature cells to accumulate and activate. This study shows that IL-5 is actually produced in the human nasal mucosa by antigen challenge, and it further investigates the changes in the amount of IL-5 in nasal lavage fluids after antigen challenge. Expression of mRNA for IL-5 in nasal mucosa was investigated using the reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot analysis. Among the 4 subjects with nasal allergy examined in this study, expression of mRNA for IL-5 was observed in 2 prior to antigen challenge; within 6 h after antigen challenge it was seen in 3 subjects. We also found that the amount of IL-5 in the nasal lavage fluids obtained consecutively after antigen challenge increased predominantly in the late phase, and that the number of eosinophils in the IL-5 positive group was significantly higher than that in the IL-5 negative group. These results strongly suggest that IL-5 contributes to the recruitment of eosinophils in the nasal mucosa of the subjects with nasal allergy.