Description: Thymic Stromal Lymphopoietin (TSLP) is a member of the B cell-stimulating factor family. This hemopoietic cytokine was identified from the conditioned medium of a mouse thymic stromal cell line that promoted B-cell development. TSLP is expressed in thymus, spleen, kidney, lung and bone marrow. The bioactivity of TSLP overlaps with that of IL-7, playing a key role in B cell development, as well as stimulating the growth of thymocytes and T cells. Whereas IL-7 facilitates the development of B220+/IgM- pre-B cells, TSLP promotes the development B220+/IgM+ B cells in the mouse. In addition, TSLP stimulates monocytes to produce the T cell-attracting chemokines TARC (CCL17) and MDC (CCL22). TSLP also activates dendritic cell-primed CD4 T cells to produce Th2 cytokines (e.g. IL-4, IL-5, IL-13, and TNF alpha). TSLP binds to a heterodimeric receptor complex consisting of the IL-7R alpha chain (CD127) and the TSLP-specific chain (TSLPR) to induce STAT3 and STAT5 phosphorylation. Mouse TSLP shares approximately 43% amino acid sequence identity with human TSLP. Recombinant human TSLP is a 15.0 kDa protein consisting of 121 amino acid residues.