The DTA-1 monoclonal antibody reacts with mouse GITR (glucocorticoid-induced TNFR-related gene), a 66-70 kDa co-stimulatory immune checkpoint molecule belonging to the Tumor Necrosis Factor superfamily (TNFRSF18). GITR is expressed at low levels on resting T lymphocytes and at high levels on regulatory T cells. GITR is upregulated on activated T cells where it provides co-stimulation. GITR ligand (GITRL) is found on B cells, macrophages, dendritic and endothelial cells, and is implicated in regulating both innate and adaptive immune responses. GITR is also thought to play a key role in dominant immunological self-tolerance maintained by regulatory T cells. Knockout studies in mice also suggest the role of this receptor is in the regulation of CD3-driven T cell activation and programmed cell death. The DTA-1 antibody is an agonistic antibody that is commonly used to induce GITR signaling in vivo.