Recombinant Rat APRILTumor necrosis factor ligand superfamily member 13 (TNFSF13) also known as a proliferation-inducing ligand (APRIL) is a member of the tumor necrosis factor ligand (TNF) ligand family. Nineteen cytokines have been identified as part of the TNF family on the basis of sequence, functional, and structural similarities. Family members include TNF beta (TNFSF1), TNF alpha (TNFSF2), Lymphotoxin beta (TNFSF3), OX40 Ligand (TNFSF4), CD40 Ligand (TNFSF5), Fas Ligand (TNFSF6), CD27 Ligand (TNFSF7), CD30 Ligand (TNFSF8), 4-1BB Ligand (TNFSF9), TRAIL (TNFSF10), TRANCE/RANKL (TNFSF11), TWEAK (TNFSF12), APRIL(TNFSF13), BAFF (TNFSF13B), LIGHT (TNFSF14), TL1A/VEGI (TNFSF15), and GITR Ligand (TNFSF18). APRIL/TNFSF13 is expressed by macrophages and dendritic cells. APRIL/TNFSF13 has been shown to play a role in protecting cells from undergoing apoptosis and promoting B cell development.