Ccl21

Chemokines, a subgroup of cytokines, are small (size between 8 and 10 kDa), chemotactically active proteins (signal proteins). They are common in all vertebrates, some virus types and bacteria. In humans, about 50 chemokines are currently known. A strongly conserved structural feature of all chemokines is a fixed group of cysteine residues that is stabilized by 1 or 2 disulfide bridges. This key structural position in the molecule is responsible for its fixed 3-dimensional structure.

In the CC chemokines, the cysteines follow each other directly (see figure), in the CXC chemokines they are separated (CC = acronym for cysteine-cysteine) by 1, in the CXXXC chemokines by 3 other amino acids. We show that CCL15 is processed in human synovial fluid by matrix metalloproteinases (MMPs) and serine proteases. They transmit their signals by binding to chemokine receptors via G-proteins. Some chemokines have a pro-inflammatory effect, others have a regulatory effect on the formation, homeostasis and proliferation of tissues.

CCL21, also known as C-C motif chemokine ligand 21, is a small human cytokine belonging to the CC chemokine family. The chemokine is encoded by the CCL21 gene on chromosome 9. CCL21 binds to the receptor CCR7, which is expressed on T and B cells.

CCL21 inhibits hematopoiesis and stimulates chemotaxis for thymocytes, activated T cells and dendritic cells, but not for B cells, macrophages or neutrophil granulocytes. CCL29 plays a role in the homeostasis of the "homing" of lymphocytes and dendritic cells in the secondary lymphatic organs. It is also involved in the pathogenesis of several malignant lymphoid and solid tumors.

1. Comerford I et al (2013) A myriad of functions and complex regulation of the CCR7/CCL19/CCL21 chemokine axis in the adaptive immune system. Cytokine Growth Factor Rev 24:269-223.
2. Lee KE et al (2017) Predictive significance of CCL21 and CXCL13 levels in the minor salivary glands of patients with Sjögren's syndrome. Clin Exp Rheumatol 35:234-240.
3. Mo M et al (2015) CCL21/CCR7 enhancesthe proliferation, migration, and invasion of human bladder cancer T24 cells. PLoS One 10:e0119506.
4. Sand LG et al (2016) Expression of CCL21 in Ewing sarcoma shows an inverse correlation with metastases and is a candidate target for immunotherapy. Cancer Immunol Immunother 65:995-1002.
5. Serra HM et al (2004) Is secondary lymphoid-organ chemokine (SLC/CCL21) much more than a constitutive chemokine? Allergy 59:1219-1223.
6. Shi M et al (2015) CCL21-CCR7 promotes the lymph node metastasis of esophageal squamous cell carcinoma by up-regulating MUC1. J Exp Clin Cancer Res 34:149.