C-C motif chemokine 21 (CCL21) is a 111 amino acid Cys-Cys chemokine that inhibits hemopoiesis and stimulates chemotaxis. It is also known as secondary lymphoid-tissue chemokine (SLC) and 6Ckine because it contains 6 conserved cysteines, in contrast to the 4 that are more typical of CC chemokines. CCL21 is a ligand for the G protein coupled receptor CCR7, and is chemotactic for thymocytes and activated T-cells, but not for B cells, macrophages, or neutrophils. It also binds to atypical chemokine receptor ACKR4 and mediates the recruitment of beta-arrestin to ACKR4. CCL21 recruits normal immune cells and metastasizing tumor cells to secondary lymphoid organs and shows preferential activity towards naive T-cells. CCL21 is expressed at high levels in the lymph nodes, spleen and appendix, intermediate levels in the small intestine, thyroid gland and trachea, and at low levels in the thymus, bone marrow, liver, and pancreas. Cytokines are a family of secreted proteins involved in immunoregulatory and inflammatory processes. The CC chemokines are chemotactic cytokines characterized by two adjacent cysteines that induce directed chemotaxis in nearby responsive cells. Recombinant human CCL21 from Molecular Innovations is provided as a native untagged protein. This chemokine is expressed in E. coli then processed, refolded and purified to yield the native, secreted form of the mature chemokine. >98percent pure by SDS-PAGE, HPLC, MALDI-MS and NMR analysis. CCR7 activity verified by chemotaxis using T2 cells. Add deionized water to desired volume, aliquot and freeze unused portion.