DR3, also known as APO-3, TRAMP or TNFRSF12, is a death domain-containing receptor of TNFR family, which is expressed preferentially in peripheral blood leukocytes and in the lymphocyte-enriched tissues. Its expression has been shown to be especially up-regulated in activated T cells. DR3 participates e.g. in the removal of self-reactive T cells in the thymus. The ligand for DR3 is TL1A (TNF-like ligand 1A), which is expressed in a variety of cell types (induced by inflammatory stimuli), and can also be released as a soluble factor. The TL1A/DR3 axis has been shown to costimulate T cells to produce a wide variety of cytokines and leads to T cell differentiation towards Th1 and Th17 types.