About CCL28 / MEC:
CCL28, also known as Chemokine ligand 28, and known in addition as a mucosae-associated epithelial chemokine (MEC), is a chemokine.
Chemokines are a group of small cytokines - signalling proteins that are secreted by the cells. The names of these cells come from their ability to induce directed chemotaxis in nearby cells that are responsive - these are called chemotactic cytokines. Cytokine proteins are classified as chemokines due to their behaviour and the structural characteristics that they hold. Also known for mediating chemotaxis, chemokines are around 8-10 kilodaltons in mass and usually have four cysteine residues kept in conserved locations, it’s these that allow them to form their three dimensional shape.
Many chemokines are pro-inflammatory and can be induced during an immune response to recruit cells of the immune system to the site of an infection. However, other chemokines are considered homeostatic and focus on controlling the migration of cells during normal processes of tissue development and maintenance. They are found in the vertebrates, some viruses and bacteria, but none have been found for other invertebrates.
Chemokines are classified in four main subfamilies, these are CXC, CC, CX3C, and XC. Each of these proteins take their proteins from biological effects by interacting with g-protein linked transmembrane receptors known as chemokine receptors - these are found on the surface of target cells.
CCL28 is known for regulating the chemotaxis of cells that express the chemokine receptors CCR3 and CCR10. CCL28 is created by columnar epithelial cells within the gut, lung, breast, and the salivary glands, and is able to drive the mucosal homing of T and B lymphocytes that express CCR10, and also the migration of eosinophils expressing CCR3.
This chemokine is expressed within the colon, however its levels are only increased by pro-inflammatory cytokines and certain bacterial products implying a role in effector cell recruitment to sites of specific epithelial injury. CCL28 has also been implicated in the migration of lgA-expressing cells to the mammary gland, salivary gland, intestine, and various other mucosal tissues. It has also been suggested as a potential antimicrobial agent, that could be effective against certain pathogens, like Gram negative and Gram positive bacteria, in addition to the fungus, Candida albicans.
The human CCL28 is encoded by an RNA transcript with 373 nucleotides and a gene that has four exons. The gene code for a 127-amino acid CCL28 protein with a 22-amino acid N-terminal signal peptide. Sharing a large percentage of nucleic acid identity (76%) and 83% amino acid similarity to the same molecule in mice. Analysis of sequence has shown that CCL28 is to be most similar to another CC chemokine known as CCL27.
All genes are classified into neighbourhoods. CCL28 is found upstream of the gene C5 of F34, and is suggested to be in the Polo-like Kinase family. C5 or F34 extends from a base pair of 43,486,701 to base pair 43,515,445.
What CCL28 does within the body is regulate chemotaxis of cells that express the chemokine receptors CCR3 and CCR10, making it a vital gene.