Interleukin-5 involvement in ovalbumin-induced eosinophil infiltration in mouse food-allergy model

A number of studies demonstrating the important role of interleukin-5 (IL-5) in eosinophil infiltration were reported. Antigen-induced eosinophil infiltrations to the trachea and skin were inhibited by pretreatment with monoclonal anti-IL-5 antibody. In this study, the role of IL-5 in eosinophil infiltration to the gut by oral challenge in mice is investigated. A marked eosinophil infiltration to the lamina propria was induced by oral challenge with ovalubumin (OVA) in Balb/c mice intraperitoneally sensitized with OVA, and peaked at 6 h after the oral challenge. Intraperitoneal preadministration of monoclonal anti-IL-5 antibody significantly decreased the eosinophil infiltration to the lamina propria. Furthermore, analysis by reverse transcription polymerase chain reaction (RT-PCR) demonstrated that IL-5 mRNA expression was induced in the lamina propria in an antigen-specific manner and the expression peaked at 6 h and declined thereafter. In-situ hybridization (ISH) revealed the presence of IL-5 mRNA positive cells at lesion site. As in bronchial mucosa and skin, IL-5 may play an important role in eosinophil recruitment to the lesion site in IgE mediated gut late phase reaction.