TSLP-R, also known as thymic stromal lymphopoietin protein receptor, cytokine receptor-like 2, CRL2, and IL-XR, is a type I membrane receptor that forms a functional heterodimeric complex with IL-7R to bind TSLP. The TSLP-R contains a WSXWS motif required for proper protein folding and a box1 motif important for association with the JAKs. TSLP-R has a predicted molecular weight approximately 40 kD, and two isoforms have been reported that are produced by alternative splicing. The TSLP-R is expressed preferentially in myeloid cells including dendritic cells and activated monocytes, and is weakly expressed in T cells. Expression has also been reported in heart, skeletal muscle, and kidney tissues. TSLP binding to the heterodimeric functional receptor (TSLP-R and IL-7R) activates JAK2, STAT3 and STAT5 to stimulate cell proliferation. Ligand receptor interactions haves been implicated in the development of the hematopoietic system, dendritic cell maturation, and the maintenance and polarization of human Th2 memory T cells in allergic diseases.