Bovine APRIL (A Proliferation-Inducing Ligand), also known as TNFSF13, is a member of the tumor necrosis factor (TNF) superfamily that plays a central role in B cell survival, plasma cell maintenance, and regulation of humoral immunity in cattle (Bos taurus). 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 bovine immune responses, APRIL contributes to mucosal immunity and IgA production, particularly in the respiratory and gastrointestinal tracts and the mammary gland. Dysregulated APRIL expression may be associated with chronic infection, persistent inflammation, and B cell–related diseases such as bovine leukemia virus (BLV)–associated lymphoproliferative disorders. In veterinary and translational research, bovine APRIL is of interest in studies of vaccine responses, mastitis immunity, mucosal antibody production, and comparative B cell biology, providing insight into antibody-mediated immune regulation and potential strategies to enhance protective immunity in cattle.