FOXP3 (Forkhead box protein 3) is a member of the forkhead/winged-helix family of transcriptional regulators, highly conserved across mammals, and essential for normal immune homeostasis. FOXP3 is 381 amino acids long, stably and constitutively expressed at a high level in CD25 + CD4 positive regulatory T cells, a low level in CD4-positive/CD25-negative cells, and is absent in CD4-negative/CD8-positive T cells. FOXP3 may be a master regulatory gene, and a more specific marker of regulatory T cells. Defects in the gene encoding FOXP3 protein cause the scurfy phenotype in mice. In humans FOXP3 defects play a role in IPEX syndrome (immune dysfunction, polyendocrinopathy, enteropathy, X-linked syndrome), also known as X-linked autoimmunity-allergic dysregulation (XLAAD) syndrome. Transcript variants of FOXP3 encoding different isoforms have been identified. In human breast and colon cancer cells, expression of FOXP3 is regulated by p53 in response to the DNA damage.
AIID; DIETER; Forkhead box P3; Forkhead box protein P3; Forkhead box protein P3 41 kDa form; Forkhead box protein P3, C-terminally processed; forkhead/winged helix transcription factor 3; foxp3; IPEX; JM2; PIDX; SCURFIN; scurfy; XPID