TECK Background Information Chemokines are likely to play an important role in regulating the trafficking of developing T cells within the thymus. Chemokine C-C thymus expressed chemokine (TECK), also designated chemokine ligand 25 (CCL25), small induc-ible cytokine A25, chemokine b-15 or CK b-15, is expressed predominantly in thymic dendritic cells, thymic epithelial cells and in the small intestine. TECK, a CCR9 ligand, has suppressive activity against immature subsets of myeloid progenitors which have been stimulated to proliferate by multiple growth factors. TECK delivers signals through CCR9, which is important for the nav-igation of developing thymocytes. Bone marrow pre-pro-B cells and cells capable of generating pro-B colonies in the presence of interleukin-7 and Flt-3 ligand migrate to TECK, a response lost in later stages of B cell development.
