[IPEX syndrome and human Treg cells]

CD4(+)CD25(+) T cells which have also been described as regulatory T cells (Treg), have immune inhibitory functions in the immune system. This population inhibits excessive immune responses, such as those present in patients with autoimmune disease, allergy and inflammation, and plays an important role in maintenance of immunological homeostasis. It has been demonstrated that the FOXP3 gene is a master gene for a transcriptional factor of Tregs. This finding has led to the elucidation of the Treg functions during development, differentiation and immune suppression. Either a deficiency or dysfunction of Tregs results in IPEX (immune dysregulation, polyendocrinopathy, enteropathy, and X-linked) syndrome. The clinical features of IPEX syndrome include chronic dermatitis, enteropathy characterized by severe and refractory diarrhea, and autoimmune endocrinopathy, such as early-onset insulin-dependent diabetes mellitus, thyroiditis, or both. This syndrome is also associated with various symptoms such as anemia, thrombocytopenia and nephritis which may be caused by an autoimmune response. We herein describe the clinical and molecular characteristics of patients with IPEX syndrome and also elucidate the function of human Treg cells.