Thymic stromal lymphopoietin (TSLP) is mainly produced by non-hematopoietic cells such as fibroblasts, epithelial cells and different types of stromal or stromal-like cells. It mainly affects myeloid cells, induces monocytes to release T-cell captive chemokines and enhances maturation of myeloid (CD11c+) dendritic cells. It has been shown that TSLP also activates the maturation of Langerhans cells, a specific subpopulation of dendritic cells located in the epidermis. Activation of myeloid and plasmacytoid (CD123+) dendritic cells by thymic TSLP leads to the production of regulatory T cells.TSLP signals through a heterodimeric receptor complex composed of the thymic stromal lymphocyte receptor CRLF2 and the IL-7Rα chain. Binding to STAT5 induces its phosphorylation, which in turn leads to the expression of upstream transcription factors.TSLP expression has been associated with many diseases including asthma, inflammatory arthritis, atopic dermatitis, eczema and other allergic states.