The cytokine thymic stromal lymphopoietin receptor (TSLPR) is consisting of a common γ receptor–like chain (TSLPR-γ) and a common interleukin 7 (IL-7) Rα chain that belongs to the type 1 cytokine receptor family. Transfection of TSLPR cDNA result in only low affinity binding, while cotransfection of the IL-7Rα chain cDNA shows high affinity binding. TSLP and TSLPR play a critical role in the initiation of allergic diseases in mice. The TSLP R cDNA encodes a transmembrane receptor containing 370 amino acids (aa) with two potential N-linked glycosylation sites and a cytoplasmic domain of 104 aa including a single tyrosine residue. TSLPR can mediate signaling of the signal transducer and activator of transcription 5 (Stat5) by TSLP. TSLP R is broadly expressed in the immune and hematopoietic cells, particularly in hematopoietic progenitors and myeloid cells.