Cutting edge: Expression of the NF of activated T cells in eosinophils: Regulation by IL-4 and IL-5

We report that NF-AT1 and NF-AT4 are expressed cytoplasmically in resting e osinophils, whereas NF-AT2 and NF-AT3 have not been seen. Likewise, NF-AT1 mRNA and NF-AT4 mRNA have been detected in resting eosinophils, and their l evels can be significantly up-regulated by the Th2-associated cytokines IL- 4 and IL-5. There is no detectable NF-AT protein expression in the nuclei o f resting eosinophils. However NF-ATs appear in the nuclei of IL-4-, IL-5-, or ionomycin-stimulated eosinophils. Only NF-AT1 and NF-AT4 but not NF-AT2 and NF-AT3, have translocated into the nuclei in IL-4- or IL-5-stimulated eosinophils. These findings delineate a novel pathway in the cytokine netwo rk in which Th2 lymphocytes "control" eosinophils via the release of IL-4 a nd IL-5, and activation of NF-AT in eosinophils, The findings also suggest that a later feedback "talking" may exist between eosinophils and Th2 lymph ocytes.