Macrophage Inflammatory Proteins (MIP) belong to the family of chemotactic

cytokine Cytokines () are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are produced by a broad range of cells, including immune cells like macrophages, B cell, B lymphocytes, T cell, T lymphocytes ...

s known as chemokines. In humans, there are two major forms, MIP-1α and MIP-1β, renamed CCL3 and CCL4 respectively, since 2000. However, other names are sometimes encountered in older literature, such as LD78α, AT 464.1 and GOS19-1 for human CCL3 and AT 744, Act-2, LAG-1, HC21 and G-26 for human CCL4. Other macrophage inflammatory proteins include MIP-2, MIP-3 and MIP-5.

MIP-1

MIP-1α and MIP-1β are major factors produced by

macrophage Macrophages (; abbreviated MPhi, φ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances, which do not have proteins that ...

s and

monocyte Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and monocyte-derived dendritic cells. As a part of the vertebrate innate immune system monocytes also ...

s after they are stimulated with

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

endotoxin Lipopolysaccharide (LPS), now more commonly known as endotoxin, is a collective term for components of the outermost membrane of the cell envelope of gram-negative bacteria, such as '' E. coli'' and ''Salmonella'' with a common structural archit ...

or proinflammatory cytokines such as IL-1β. But it appears that they can be expressed by all hematopoietic cells and some tissue cells such as fibroblasts, epithelial cells, vascular smooth muscle cells or platelets upon activation. They are crucial for immune responses towards infection and inflammation. CCL3 and CCL4 can bind to extracellular proteoglycans, which is not necessary for their function but it can enhance their bioactivity. The biological effect is carried out through ligation of chemokine receptors CCR1 (ligand CCL3) and

CCR5 C-C chemokine receptor type 5, also known as CCR5 or CD195, is a protein on the surface of white blood cells that is involved in the immune system as it acts as a receptor for chemokines. In humans, the ''CCR5'' gene that encodes the CCR5 p ...

(ligands CCL3 and CCL4) and the signal is then transferred into the cell, thus these cytokines affect any cell that has these receptors. The main effect is inflammatory and mainly consists of

chemotaxis Chemotaxis (from ''chemical substance, chemo-'' + ''taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell organism, single-cell or multicellular organisms direct thei ...

and transendothelial migration but cells can be activated to release of some bioactive molecules also. These chemokines affect

s, T lymphocytes,

dendritic cell A dendritic cell (DC) is an antigen-presenting cell (also known as an ''accessory cell'') of the mammalian immune system. A DC's main function is to process antigen material and present it on the cell surface to the T cells of the immune system ...

s, NK cells and

platelet Platelets or thrombocytes () are a part of blood whose function (along with the coagulation#Coagulation factors, coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a thrombus, blood clot. Platelets have no ...

s. They, too, activate human

granulocyte Granulocytes are cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear, that i ...

s (

neutrophil Neutrophils are a type of phagocytic white blood cell and part of innate immunity. More specifically, they form the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. Their functions vary in differe ...

s, eosinophils and basophils) which can lead to acute neutrophilic inflammation. They also induce the synthesis and release of other pro-inflammatory cytokines such as

interleukin 1 The Interleukin-1 family (IL-1 family) is a group of 11 cytokines that plays a central role in the regulation of immune and inflammatory responses to infections or sterile insults. Discovery Discovery of these cytokines began with studies on t ...

(IL-1), IL-6 and TNF-α from

fibroblast A fibroblast is a type of cell (biology), biological cell typically with a spindle shape that synthesizes the extracellular matrix and collagen, produces the structural framework (Stroma (tissue), stroma) for animal Tissue (biology), tissues, and ...

s and macrophages. The genes for CCL3 and CCL4 are both located on human

chromosome 17 Chromosome 17 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 17 spans more than 84 million base pairs (the building material of DNA) and represents between 2.5 and 3% of the total DN ...

and on murine chromosome 11. They are produced by many cells, particularly macrophages, dendritic cells, and lymphocytes. MIP-1 are best known for their chemotactic and proinflammatory effects but can also promote homeostasis. Biophysical analyses and mathematical modelling has shown that MIP-1 reversibly forms a polydisperse distribution of rod-shaped polymers in solution. Polymerization buries receptor-binding sites of MIP-1, thus depolymerization mutations enhance MIP-1 to arrest monocytes onto activated human endothelium. MIP-1γ is another macrophage inflammatory protein and according to the new nomenclature is named CCL9. It is produced mainly by follicle-associated

epithelial cells Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

and is responsible for chemotaxis of dendritic cells and macrophages into

Peyer's patch Peyer's patches or aggregated lymphoid nodules are organized lymphoid follicles, named after the 17th-century Swiss anatomist Johann Conrad Peyer. * Reprinted as: * Peyer referred to Peyer's patches as ''plexus'' or ''agmina glandularum'' (cl ...

es in gut through binding of CCR1. MIP-1δ or MIP-5 (CCL15) binds also CCR1 and CCR3.

MIP-2

MIP-2 belongs to the CXC chemokine family, is named CXCL2 and acts through binding of CXCR1 and CXCR2. It is produced mainly by macrophages, monocytes and epithelial cells and is responsible for chemotaxis to the source of inflammation and activation of neutrophils.

MIP-3

There are two chemokines in the MIP-3 group. MIP-3α (CCL20) and MIP-3β (CCL19). MIP-3α is binding to receptor CCR6. CCL20 is produced by mucosa and skin by activated epithelial cells and attracts Th17 cells to the site of inflammation. It is also produced by Th17 cells themselves. It further attracts activated

B cell B cells, also known as B lymphocytes, are a type of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted or inserted into the plasm ...

s, memory

T cell T cells (also known as T lymphocytes) are an important part of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell ...

s and immature

s and has part in migration of these cells in

secondary lymphoid organs The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphoid organs, lympha ...

. Mature dendritic cells down-regulate CCR6 and up-regulate CCR7, which is receptor for MIP-3β. MIP-3β ( CCL19) is produced by stromal cells in T-cell zones of

and binds to CCR7 receptor through which attracts mature dendritic cells to

lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...

s. It is also produced by dendritic cells and attracts also naive T lymphocytes and B lymphocytes to homing into the lymph node, where

antigen In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

s can be presented to them by dendritic cells.

MIP-5

MIP-5 (sometimes called MIP-1δ) or CCL15 binds to receptors CCR1 and CCR3. It has chemotactic properties for monocytes and eosinophils and is expressed by macrophages, basophils and some tissue cells. It is proposed to have a role in pathology of

asthma Asthma is a common long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wh ...

References

External links