Thymic stromal lymphopoietin (TSLP) is produced mainly by non-hematopoietic cells such as fibroblasts, epithelial cells and different types of stromal or stromal-like cells. It mainly impacts myeloid cells and induces the release of T cell-attracting chemokines from monocytes and enhances the maturation of myeloid (CD11c ) dendritic cells. TSLP has also been shown to activate the maturation of a specific subset of dendritic cells located within the epidermis, called Langerhans cells. Within the thymus TSLP activation of both myeloid and plasmacytoid (CD123 ) dendritic cells results in the production of regulatory T cells. TSLP signals through a heterodimeric receptor complex composed of the thymic stromal lymphopoietin receptor CRLF2 and the IL-7R alpha chain. After binding STAT5 phosphorylation is induced resulting in the expression of upstream transcription factors. TSLP expression is linked to many disease states including asthma, inflammatory arthritis, atopic dermatitis, and eczema and other allergic states.