IL17A (interleukin-17A) is a cytokine produced by activated T cells that regulates NFKB and MAPK kinases. IL17A has pro-inflammatory functions and is involved in host defense. High expression of the protein is correlated with autoimmune and inflammatory diseases including multiple sclerosis, psoriasis, rheumatoid arthritis. IL17A expression is also associated with stroke and depression, accelerated inflammation and degeneration in Parkinson’s disease, as well as central nervous system infections. In immunohistochemistry, IL17A has variable secretory positivity in serum, gastrointestinal tissue, reproductive tissues, and in infiltrating T lymphocytes at sites of inflammation and tissues in various tumorigenic and disease states. References: Acta Neuropathol. 2015 May;129(5):625-37, PMID: 25716179; Brain Behav Immun. 2019 Jul 24. pii: S0889-1591(19)30539-2, PMID: 31351185; Ann Dermatol. 2014 Apr; 26(2): 203–208, PMID: 24882975;