Chemokine ligand 9 (CCL9) is a small cytokine

Cytokine

Cytokines are small cell-signaling protein molecules that are secreted by the glial cells of the nervous system and by numerous cells of the immune system and are a category of signaling molecules used extensively in intercellular communication...

 belonging to the CC chemokine

Chemokine

Chemokines are a family of small cytokines, or proteins secreted by cells. Their name is derived from their ability to induce directed chemotaxis in nearby responsive cells; they are chemotactic cytokines...

 family. It is also called macrophage inflammatory protein-1 gamma (MIP-1γ), macrophage inflammatory protein-related protein-2 (MRP-2) and CCF18 , that has been described in rodents. CCL9 has also been previously designated CCL10, although this name is no longer in use. It is secreted by follicle-associated epithelium

Epithelium

Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...

 (FAE) such as that found around Peyer's patches, and attracts dendritic cell

Dendritic cell

Dendritic cells are immune cells forming part of the mammalian immune system. Their main function is to process antigen material and present it on the surface to other cells of the immune system. That is, dendritic cells function as antigen-presenting cells...

s that possess the cell surface molecule CD11b

Integrin alpha M

Integrin alpha M is one protein subunit that forms the heterodimeric integrin alpha-M beta-2 molecule, also known as macrophage-1 antigen or complement receptor 3 . ITGAM is also known as CR3A, and cluster of differentiation molecule 11B...

 and the chemokine receptor

Chemokine receptor

Chemokine receptors are cytokine receptors found on the surface of certain cells, which interact with a type of cytokine called a chemokine. There have been 19 distinct chemokine receptors described in mammals...

 CCR1

CC chemokine receptors

CC chemokine receptors are integral membrane proteins that specifically bind and respond to cytokines of the CC chemokine family. They represent one subfamily of chemokine receptors, a large family of G protein-linked receptors that are known as seven transmembrane proteins since they span the...

. CCL9 can activate osteoclast

Osteoclast

An osteoclast is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone . This process is known as bone resorption. Osteoclasts were discovered by Kolliker in 1873...

s through its receptor CCR1 (the most abundant chemokine receptor found on osteoclasts) suggesting an important role for CCL9 in bone resorption

Bone resorption

Bone resorption is the process by which osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood....

. CCL9 is constitutively expressed in macrophage

Macrophage

Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...

s and myeloid

Myeloid

The term myeloid suggests an origin in the bone marrow or spinal cord, or a resemblance to the marrow or spinal cord.In hematopoiesis, the term "myeloid cell" is used to describe any leukocyte that is not a lymphocyte...

 cells. The gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

 for CCL9 is located on chromosome

Chromosome

A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

11 in mice.