IL-3 and TNFα increase Thymic Stromal Lymphopoietin Receptor (TSLPR) expression on eosinophils and enhance TSLP-stimulated degranulation

Eosinophil mRNA expression of TSLPR and IL-7Rα was examined by real-time quantitative PCR of human eosinophils treated with TNFα and IL-5 family cytokines, and TSLPR surface expression on eosinophils was analyzed by flow cytometry. Eosinophils were stimulated with TSLP (with and without pre-activation with TNFα and IL-3) and evaluated for release of eosinophil derived neurotoxin (EDN), phosphorylation of STAT5, and survival by trypan blue exclusion. A blocking antibody for TSLPR was used to confirm the specificity of TSLP mediated signaling on eosinophil degranulation.Eosinophil expression of cell surface TSLPR and TSLPR mRNA was upregulated by stimulation with TNFα and IL-3. TSLP stimulation resulted in release of EDN, phosphorylation of STAT5 as well as promotion of viability and survival. TSLP-stimulated eosinophil degranulation was inhibited by a functional blocking antibody to TSLPR. Pre-activation of eosinophils with TNFα and IL-3 promoted eosinophil degranulation at lower concentrations of TSLP stimulation.This study demonstrates that eosinophils are activated by TSLP and that eosinophil degranulation in response to TSLP may be enhanced on exposure to cytokines present in allergic inflammation, indicating that the eosinophil has the capacity to participate in TSLP-driven allergic responses.Thymic stromal lymphopoietin (TSLP) is a cytokine which plays a key role in allergic diseases such as asthma, atopic dermatitis, allergic rhinitis, nasal polyposis, and chronic allergic keratoconjunctivis [1-5]. TSLP is a member of the hematopoietic cytokine family that includes a number of cytokines important in allergic disease including IL-2, IL-4, IL-7, and IL-13. TSLP binds with high affinity to a heterodimeric receptor consisting of the IL-7 receptor - alpha chain (IL-7Rα) and TSLPR (TSLP receptor also known as cytokine receptor-like 2, CRL2). As a member of the hematopoietin receptor family, signaling through activation of TSLPR results in downstream phosphorylation