PROTECTIVE ROLES OF EOSINOPHILS IN NIPPOSTRONGYLUS-BRASILIENSIS INFECTION

Nippostrongylus brasiliensis infection is characterized by blood and t issue eosinophilia induced by interleukin (IL)-5 secreted from CD4+ T cells. However, it is still obscure whether eosinophils play an import ant role in the protection against N. brasiliensis infection. In this study we attempted to determine whether the in vivo environment of IL- 5 transgenic mice, characterized by high eosinophil production, could affect the worm burden after N. brasiliensis infection. Kinetic studie s on the infection demonstrated a significantly lower worm recovery fr om the intestine of IL-5 transgenic mice compared to age-matched backg round controls. This tendency was also observed at the lung stage of t he infection. Furthermore, with respect to elevation of the serum IgE concentration, the peak level was observed at 2 weeks after infection in infected background control mice with four times higher concentrati ons than those of uninfected mice. In contrast, the increase of IgE co ncentration in IL-5 transgenic mice was very limited and low. The adop tive transfer of eosinophils from IL-5 transgenic mice into background control animals resulted in the reduction of worm recovery from the l ungs, suggesting that eosinophils play a key role in the protection ag ainst migrating larvae of N. brasiliensis. These results indicate that the innate high level of eosinophils due to constitutive production o f IL-5 augments immunity against N. brasiliensis infection.