Mouse APRIL (A Proliferation-Inducing Ligand), also known as TNFSF13, is a member of the tumor necrosis factor (TNF) superfamily and plays a key role in B cell biology and humoral immunity. APRIL is produced primarily by myeloid cells such as monocytes, macrophages, and dendritic cells, as well as by some epithelial and stromal cells, and it signals through the receptors TACI (TNFRSF13B) and BCMA (TNFRSF17) to promote B cell survival, plasma cell maintenance, and immunoglobulin class switching. In mice, APRIL contributes to the regulation of antibody production, long-lived plasma cell persistence in the bone marrow, and mucosal IgA responses. Dysregulated APRIL expression has been associated with autoimmune disease models, B cell malignancies, and chronic inflammatory conditions. In biomedical research, mouse APRIL is widely studied in models of systemic lupus erythematosus (SLE), rheumatoid arthritis, multiple myeloma, and antibody-mediated immune responses, where it serves as an important mediator of B cell–driven immunity and a potential therapeutic target for modulating pathological antibody production.