Rabbit APRIL (A Proliferation-Inducing Ligand), also known as TNFSF13, is a member of the tumor necrosis factor (TNF) superfamily that plays a key role in B cell survival, plasma cell maintenance, and regulation of humoral immunity in rabbits (Oryctolagus cuniculus). APRIL is produced primarily by monocytes, macrophages, dendritic cells, and certain epithelial and stromal cells, and it signals through the receptors TACI (TNFRSF13B) and BCMA (TNFRSF17) to promote B cell maturation, immunoglobulin class switching, and the persistence of long-lived antibody-secreting plasma cells in lymphoid tissues and bone marrow. In rabbits, which are widely used for polyclonal and monoclonal antibody production, APRIL contributes to robust antibody responses and maintenance of humoral immunity, including mucosal IgA production. Dysregulated APRIL expression may be associated with chronic inflammation, autoimmune-like conditions, or B cell–related proliferative disorders in experimental models. In biomedical and translational research, rabbit APRIL is of particular interest in studies of vaccine immunogenicity, antibody production, mucosal immunity, and comparative B cell biology, where understanding APRIL-mediated signaling provides insight into regulation of antibody responses and potential strategies to modulate humoral immunity.