Interleukin 5 (IL5) is an

interleukin Interleukins (ILs) are a group of cytokines (secreted proteins and signal molecules) that are expressed and secreted by white blood cells (leukocytes) as well as some other body cells. The human genome encodes more than 50 interleukins and related ...

produced by type-2

T helper cell The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are consider ...

s and

mast cells A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a ...

Function

Through binding to the

interleukin-5 receptor The interleukin-5 receptor is a type I cytokine receptor. It is a heterodimer of the interleukin 5 receptor alpha subunit and CSF2RB. The IL-5 receptor (IL-5R) belongs to the type I cytokine receptor family and is a heterodimer composed of two ...

, interleukin 5 stimulates B cell growth and increases immunoglobulin secretion - primarily IgA. It is also a key mediator in

eosinophil Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells (WBCs) and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. A ...

activation.

Structure

IL-5 is a 115-

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...

(in human, 133 in the mouse) -long TH2

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 autocrin ...

that is part of the hematopoietic family. Unlike other members of this

family (namely

interleukin 3 Interleukin 3 (IL-3) is a protein that in humans is encoded by the ''IL3'' gene localized on chromosome 5q31.1. Sometimes also called colony-stimulating factor, multi-CSF, mast cell growth factor, MULTI-CSF, MCGF; MGC79398, MGC79399: the protein ...

and

GM-CSF Granulocyte-macrophage colony-stimulating factor (GM-CSF), also known as colony-stimulating factor 2 (CSF2), is a monomeric glycoprotein secreted by macrophages, T cells, mast cells, natural killer cells, endothelial cells and fibroblasts tha ...

), this glycoprotein in its active form is a homodimer.

Tissue expression

The IL-5

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 ...

is located on

chromosome 11 Chromosome 11 is one of the 23 pairs of chromosomes in humans. Humans normally have two copies of this chromosome. Chromosome 11 spans about 135 million base pairs (the building material of DNA) and represents between 4 and 4.5 percent of the tot ...

in the mouse, and chromosome 5 in humans, in close proximity to the genes encoding IL-3, IL-4, and

granulocyte-macrophage colony-stimulating factor Granulocyte-macrophage colony-stimulating factor (GM-CSF), also known as colony-stimulating factor 2 (CSF2), is a monomeric glycoprotein secreted by macrophages, T cells, mast cells, natural killer cells, endothelial cells and fibroblasts that ...

(

), which are often co-expressed in TH2 cells. Interleukin-5 is also expressed by

eosinophils Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells (WBCs) and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. A ...

and has been observed in the

of asthmatic airways by immunohistochemistry. IL-5 expression is regulated by several

transcription factors In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The fun ...

including

GATA3 GATA3 is a transcription factor that in humans is encoded by the ''GATA3'' gene. Studies in animal models and humans indicate that it controls the expression of a wide range of biologically and clinically important genes. The GATA3 transcription ...

Clinical significance

Interleukin-5 has long been associated with the cause of several allergic diseases including

allergic rhinitis Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, i ...

and

asthma Asthma is a 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 wheezing, co ...

, wherein a large increase in the number of circulating, airway tissue, and induced sputum eosinophils have been observed. Given the high concordance of eosinophils and, in particular, allergic asthma pathology, it has been widely speculated that eosinophils have an important role in the pathology of this disease. Drugs that target IL-5 are

mepolizumab Mepolizumab, sold under the brand name Nucala, is a humanized monoclonal antibody used for the treatment of severe eosinophilic asthma, eosinophilic granulomatosis, and hypereosinophilic syndrome (HES). It recognizes and blocks interleukin-5 ( ...

and

reslizumab Reslizumab is a humanized monoclonal antibody against human interleukin-5 (IL-5). Reslizumab binds specifically to IL-5, a key cytokine responsible for the differentiation, maturation, recruitment and activation of human eosinophils. By binding ...

Effect on eosinophils

Eosinophils are terminally differentiated

granulocytes 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. They ha ...

found in most

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...

. The principal role of these cells, in a healthy host, is the elimination of antibody bound parasites through the release of cytotoxic granule proteins. Given that eosinophils are the primary IL-5Rα-expressing cells, it is not surprising that this cell type responds to IL-5. In fact, IL-5 was originally discovered as an eosinophil colony-stimulating factor, is a major regulator of eosinophil accumulation in tissues, and can modulate eosinophil behavior at every stage from maturation to survival.

Mepolizumab Mepolizumab, sold under the brand name Nucala, is a humanized monoclonal antibody used for the treatment of severe eosinophilic asthma, eosinophilic granulomatosis, and hypereosinophilic syndrome (HES). It recognizes and blocks interleukin-5 ( ...

is a monoclonal antibody antagonist IL-5 which can reduce excessive eosinophilia. In

Hodgkin lymphoma Hodgkin lymphoma (HL) is a type of lymphoma, in which cancer originates from a specific type of white blood cell called lymphocytes, where multinucleated Reed–Sternberg cells (RS cells) are present in the patient's lymph nodes. The condition w ...

, for instance, the typically-observed eosinophilia is thought to be attributable to an increased production of IL-5.

Interactions

Interleukin 5 has been shown to interact with

Interleukin 5 receptor alpha subunit Interleukin 5 receptor, alpha (IL5RA) also known as CD125 (Cluster of Differentiation 125) is a subunit of the Interleukin-5 receptor. IL5RA also denotes its human gene. Function The protein encoded by this gene is an interleukin 5 specific su ...

Receptors

The IL-5 receptor is composed of an α and a βc chain. The α subunit is specific for the IL-5 molecule, whereas the βc subunit also recognised by

(IL3) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Glycosylation of the Asn196 residue of the Rα subunit appears to be essential for binding of IL-5.

References

External links

* {{Authority control Interleukins