Interleukin-5 Preferentially Recruits Eosinophils from Vessels in Nasal Mucosa

Interleukin-5 (IL-5), initially described as possessing eosinophil differentiating and proliferating activity, has now been shown to exert its effects on mature eosinophils. To investigate the ability of recombinant human IL-5 (rhIL-5) to cause the migration of eosinophils in the nasal mucosa in vivo, we compared the eosinophil counts in nasal mucosa without and after the nasal application of rhIL-5. In addition, the percentages of eosinophils in leukocytes within the vascular lumens in the nasal mucosa were counted to determine whether IL-5 recruited eosinophils from the vessels. The total number of eosinophils in both the epithelium and lamina propria, as well as the percentage of eosinophils in leukocytes within the lumens of vessels in the nasal mucosa after the application of IL-5, were higher than those in control nasal mucosa. Conversely, neither the number of neutrophils in the nasal mucosa nor the percentages of neutrophils in vessels differed between the two groups of nasal mucosa. The results strongly suggest that IL-5 preferentially recruits eosinophils from vessels into the lamina propria.