TNFSF18 is a single-pass type II membrane protein. It is expressed at high levels in the small intestine, ovary, testis, kidney and endothelial cells. TNFSF18 cytokine binds to TNFRSF18/AITR/GITR. It regulates T-cell responses, and functions as costimulator and lower the threshold for T-cell activation and T-cell proliferation. It is Important for interactions between activated T-lymphocytes and endothelial cells and Promotes leukocyte adhesion to endothelial cells. TNFSF18 mediates activation of NF-kappa-B. As Triggers increased phosphorylation of STAT1 and up-regulates expression of VCAM1 and ICAM1. It also regulates migration of monocytes from the splenic reservoir to sites of inflammation.