Interleukin 23 subunit alpha

Interleukin-23 subunit alpha is a is_associated_with::protein that in humans is encoded by the IL23A is_associated_with::gene. IL-23 is produced by is_associated_with::dendritic cells and is_associated_with::macrophages.

Interleukin-23 is a is_associated_with::heterodimeric cytokine composed of an IL-12p40 subunit that is shared with is_associated_with::IL-12 and the IL-23p19 subunit. A functional receptor for IL-23 (the IL-23 receptor) has been identified and is composed of IL-12R β1 and IL-23R.

Function
IL-23 is an important part of the inflammatory response against is_associated_with::infection. It promotes upregulation of the matrix is_associated_with::metalloprotease is_associated_with::MMP9, increases is_associated_with::angiogenesis 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. Th17 cells represent the most prominent T cell subset that responds to IL-23, although IL-23 has been implicated in inhibiting the development of is_associated_with::regulatory T cell development in the intestine. Th17 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, is_associated_with::TNF-alpha, NOS-2, and is_associated_with::chemokines resulting in inflammation.

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 (EAE) and inflammatory bowel disease highlighting the importance of IL-23 in the inflammatory pathway.

Discovery
A computational search for IL-12 is_associated_with::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.