Ferret 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 ferrets (Mustela putorius furo). 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 ferrets, APRIL contributes to systemic and mucosal antibody responses, particularly in respiratory tissues, which are central to ferret models of human viral infection. Expression of APRIL may increase during viral challenge, vaccination, or inflammatory stimulation, supporting adaptive immune responses and antibody production. In biomedical and translational research, ferret APRIL is of particular interest in studies of influenza, SARS-CoV-2, and other respiratory pathogens, as well as in vaccine efficacy and comparative B cell immunology research. Characterizing APRIL signaling in ferrets provides valuable insight into antibody-mediated immunity and the regulation of humoral responses in a widely used model of human infectious disease.