Chemokine (C-C motif) ligand 21 (CCL21) is a small cytokine belonging to the CC chemokine family. This chemokine is also known as 6Ckine (because it has six conserved cysteine residues instead of the four cysteines typical to chemokines), exodus-2, and secondary lymphoid-tissue chemokine (SLC).[5][6][7] CCL21 elicits its effects by binding to a cell surface chemokine receptor known as CCR7.[8] The main function of CCL21 is to guide CCR7 expressing leukocytes to the secondary lymphoid organs, such as lymph nodes and Peyer´s patches.[9]
^Comerford I, Harata-Lee Y, Bunting MD, Gregor C, Kara EE, McColl SR (June 2013). "A myriad of functions and complex regulation of the CCR7/CCL19/CCL21 chemokine axis in the adaptive immune system". Cytokine & Growth Factor Reviews. 24 (3): 269–283. doi:10.1016/j.cytogfr.2013.03.001. PMID23587803.