Binds to FN14 and possibly also to TNRFSF12/APO3. Weak inducer of apoptosis in some cell types. Mediates NF-kappa-B activation. Promotes angiogenesis and the proliferation of endothelial cells. Also involved in induction of inflammatory cytokines. Promotes IL8 secretion. Homotrimer (Probable). Interacts with the angiogenic factor AGGF1/VG5Q. Highly expressed in adult heart, pancreas, skeletal muscle, brain, colon, small intestine, lung, ovary, prostate, spleen, lymph node, appendix and peripheral blood lymphocytes. Low expression in kidney, testis, liver, placenta, thymus and bone marrow. Also detected in fetal kidney, liver, lung and brain. The soluble form derives from the membrane form by proteolytic processing. Based on a readthrough transcript which may produce a TWE-PRIL (TNFSF12-TNFSF13) fusion protein. Expressed at protein level in primary T-lymphocytes and monocytic cell lines. Belongs to the tumor necrosis factor family.