Interleukin 23 subunit alpha
Interleukin-23 subunit alpha is a protein that in humans is encoded by the "IL23A" gene. IL-23 is produced by dendritic cells and macrophages. Interleukin-23 is a heterodimeric cytokine composed of an IL-12p40 subunit that is shared 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 infection. It promotes upregulation of the matrix metalloprotease MMP9, increases 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. T17 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 development in the intestine. T17 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, NOS-2, and chemokines 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 (EAE) and inflammatory bowel disease 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.