Interleukin-23 subunit alpha is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that in humans is encoded by the ''IL23A''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. The protein is also known as IL-23p19. It is one of the two subunits of the cytokine Interleukin-23. Interleukin-23 (IL-23) is a

heterodimer In biochemistry, a protein dimer is a macromolecular complex or multimer formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ...

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 ...

composed of an Interleukin 23 alpha subunit and an IL-12p40 subunit. The IL-12p40, also known as

Interleukin 12 subunit beta Subunit beta of interleukin 12 (also known as IL-12B, natural killer cell stimulatory factor 2, cytotoxic lymphocyte maturation factor p40, or interleukin-12 subunit p40) is a protein subunit that in humans is encoded by the IL12B gene. IL-12B is ...

, is used by both IL-23 (where it partners with IL-23p19) and IL-12 (where it partners with IL-12A). A functional

receptor Receptor may refer to: * Sensory receptor, in physiology, any neurite structure that, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and respond ...

for IL-23 (the IL-23 receptor) has been identified and is composed of IL-12R β1 and IL-23R.

Function

Produced by

dendritic cells 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 ...

and

macrophages 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 ...

, IL-23 is an important part of the

inflammatory response Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

against

infection An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...

. It promotes upregulation of the matrix metalloprotease MMP9, increases

angiogenesis Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature mainly by processes of sprouting and ...

and reduces CD8+ T-cell infiltration into tumours. IL-23 mediates its effects on both innate and adaptive arms of the immune system that express the IL-23 receptor. T_h17 cells represent the most prominent T cell subset that responds to IL-23, although IL-23 has been implicated in inhibiting the development of

regulatory T cell The regulatory T cells (Tregs or Treg cells), formerly known as suppressor T cells, are a subpopulation of T cells that modulate the immune system, maintain immune tolerance, tolerance to self-antigens, and prevent autoimmune disease. Treg ...

development in the intestine. T_h17 cells produce IL-17, a proinflammatory cytokine that enhances T cell priming and stimulates the production of other proinflammatory molecules such as IL-1, IL-6,

TNF-alpha Tumor necrosis factor (TNF), formerly known as TNF-α, is a chemical messenger produced by the immune system that induces inflammation. TNF is produced primarily by activated macrophages, and induces inflammation by binding to its receptors o ...

, NOS-2, and

chemokines Chemokines (), or chemotactic cytokines, are a family of small cytokines or signaling proteins secreted by cells that induce directional movement of leukocytes, as well as other cell types, including endothelial and epithelial cells. In addit ...

resulting in inflammation. The expression of IL23A is decreased after AHR knockdown in THP-1 cells and primary mouse macrophages.

Clinical significance

Knockout mice deficient in either p40 or p19, or in either subunit of the IL-23 receptor (IL-23R and IL12R-β1) develop less severe symptoms of

experimental autoimmune encephalomyelitis Experimental autoimmune encephalomyelitis, sometimes experimental allergic encephalomyelitis (EAE), is an animal model of brain inflammation. It is an inflammatory demyelinating disease of the central nervous system (CNS). It is mostly used with r ...

(EAE) and

inflammatory bowel disease Inflammatory bowel disease (IBD) is a group of inflammatory conditions of the colon and small intestine, with Crohn's disease and ulcerative colitis (UC) being the principal types. Crohn's disease affects the small intestine and large intestine ...

highlighting the importance of IL-23 in the inflammatory pathway.

Discovery

A computational search for IL-12 homologue genes found p19, a gene that encodes a cytokine chain. Experimental work revealed that p19 formed a heterodimer by binding to p40, a subunit of IL-12. This new heterodimer was named IL-23. Knockdown of AHR decreases the expression of IL23A in THP-1 cells and primary macrophage.

Pharmacology

Several biologic drugs work by targeting IL-23A.

Ustekinumab Ustekinumab, sold under the brand name Stelara among others, is a monoclonal antibody medication used for the treatment of Crohn's disease, ulcerative colitis, Psoriasis, plaque psoriasis and psoriatic arthritis, targeting both IL-12 and IL-23. ...

, a

monoclonal antibody A monoclonal antibody (mAb, more rarely called moAb) is an antibody produced from a cell lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell. Monoclonal antibodie ...

targeting both IL-12 and IL-23 and used to treat

plaque psoriasis Psoriasis is a long-lasting, noncontagious autoimmune disease characterized by patches of abnormal skin. These areas are red, pink, or purple, dry, itchy, and scaly. Psoriasis varies in severity from small localized patches to complete b ...

psoriatic arthritis Psoriatic arthritis (PsA) is a long-term inflammatory arthritis that may occur in some people affected by the autoimmune disease psoriasis. The classic features of psoriatic arthritis include dactylitis (sausage-like swelling of the fingers ...

, and

Crohn's disease Crohn's disease is a type of inflammatory bowel disease (IBD) that may affect any segment of the gastrointestinal tract. Symptoms often include abdominal pain, diarrhea, fever, abdominal distension, and weight loss. Complications outside of the ...

, launched in the United States under the brand name Stelara.

Risankizumab Risankizumab, sold under the brand name Skyrizi ( ), is a humanized monoclonal antibody used for the treatment of plaque psoriasis, psoriatic arthritis, Crohn's disease, and ulcerative colitis. It is designed to target interleukin 23A (IL-23A) ...

is another monoclonal antibody that targets IL-23A and is approved to treat plaque psoriasis, psoriatic arthritis, Crohn's disease, and

ulcerative colitis Ulcerative colitis (UC) is one of the two types of inflammatory bowel disease (IBD), with the other type being Crohn's disease. It is a long-term condition that results in inflammation and ulcers of the colon and rectum. The primary sympto ...

Function

Clinical significance

Discovery

Pharmacology

References

Further reading