Chemokine (C-C motif) ligand 21 (CCL21) is a small
cytokine
Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in a ...
belonging to the CC
chemokine
Chemokines (), or chemotactic cytokines, are a family of small cytokines or Cell signaling, signaling proteins secreted by Cell (biology), cells that induce directional movement of leukocytes, as well as other cell types, including endothelial a ...
family. This chemokine is also known as 6Ckine (because it has six conserved
cysteine
Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile.
When present as a deprotonated catalytic residue, s ...
residues instead of the four cysteines typical to chemokines), exodus-2, and secondary lymphoid-tissue chemokine (SLC).
The
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
for CCL21 is located on human
chromosome 9. CCL21 elicits its effects by binding to a cell surface
chemokine receptor
Chemokine receptors are cytokine receptors found on the surface of certain cells that interact with a type of cytokine called a chemokine. There have been 20 distinct chemokine receptors discovered in humans. Each has a rhodopsin-like 7- tr ...
known as
CCR7
C-C chemokine receptor type 7 is a protein that in humans is encoded by the ''CCR7'' gene. Two ligands have been identified for this receptor: the chemokines (C-C motif) ligand 19 (CCL19/ELC) and (C-C motif) ligand 21 (CCL21).
CCR7 has also recen ...
.
In human lymph nodes, the fibroblastic reticular cells (FRCs) express CCL21 as a chemoattractant to guide naive, CCR7 expressing T cells to the T cell zone.
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Cytokines
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