Swine APRIL (A Proliferation-Inducing Ligand), also known as TNFSF13, is a member of the tumor necrosis factor (TNF) superfamily that plays an important role in B cell survival, plasma cell maintenance, and regulation of humoral immunity in pigs (Sus scrofa). 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 swine, APRIL contributes to mucosal immunity, including IgA production in the respiratory and gastrointestinal tracts, which is particularly relevant for defense against enteric and respiratory pathogens. Dysregulated APRIL expression may be associated with chronic infection, persistent inflammation, or B cell dysregulation in porcine disease models. In veterinary and translational research, swine APRIL is of interest in studies of vaccine-induced antibody responses, mucosal immunity, porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza, and other infectious disease models, as well as in comparative immunology research due to physiological similarities between pigs and humans. Characterizing APRIL signaling in swine provides valuable insight into antibody-mediated immunity and strategies to enhance protective immune responses in both agricultural and biomedical settings.