APRIL (a proliferation-inducingligand), also known as TNFSF13, TALL2, TRDL1, and CD256, is a member of the TNF ligand superfamily. It is synthesized as a32 kDa proprotein which is cleaved by furin in the Golgi to release the active 17 kDa soluble molecule. Secreted human APRIL, which consists almost entirely ofa single TNF homology domain, shares 85% amino acid sequence identity with mouse and rat APRIL. Both APRIL and its close relative BAFF bind and signalthrough the TNF superfamily receptors TACI and BCMA, while BAFF additionally functions through BAFF R. APRIL binds to heparan sulfateproteoglycans (HSPGs) independently of its binding to TACI and BCMA. APRIL can form bioactive heterotrimers withBAFF, and these circulate in the serum of patients with rheumatic immune disorders. APRIL enhances the proliferation and survival of plasma cells andalso promotes T cell-dependenthumoral responses. APRIL levels are elevated inthe serum during coronary artery disease, and it is also elevated in many cancers primarily due to expression by tumor-infiltratingneutrophils.