GITR or TNFRSF18 is a 241aa novel member of the tumor necrosis factor receptor superfamily and a receptor for TNFSF18. It has three extracytoplasmic cysteine-rich pseudorepeats, a small cytoplasmic tail and a DEATH domain. It is an essential regulator of immune responses to self tissues and pathogens and plays a key role in dominant immunological self-tolerance maintained by CD25 (+) CD4 (+) regulatory T cells. It is known to be involved in regulation of CD3-driven T-cell activation and programmed cell death and also in interactions between activated T-lymphocytes and endothelial cells. In mammalian cells it mediates NF-kappa-B activation via TRAF2 and modulates T lymphocyte survival in peripheral tissues. It is mostly expressed in lymph node, peripheral blood leukocytes and weakly expressed in spleen. GITR and its ligand are also known to be involved in atopic dermatitis.