TNFSF13, also known as A Proliferation-Inducing Ligand (APRIL), is a TNF superfamily cytokine that serves as a crucial regulator of B cell biology and humoral immunity 1. The protein binds to receptors TNFRSF13B/TACI and TNFRSF17/BCMA, playing essential roles in B cell survival, proliferation, and immunoglobulin class switching 2. APRIL promotes plasma cell generation and survival, making it fundamental for antibody production 3. However, dysregulated APRIL signaling contributes to autoimmune pathogenesis, particularly in IgA nephropathy where it mediates production of galactose-deficient IgA1 and pathogenic immune complexes that deposit in glomeruli 43. The protein also activates NF-κB signaling pathways through interaction with HSPG2, promoting fibroblast proliferation and inflammatory responses in fibrotic diseases 5. Therapeutically, APRIL represents an attractive target for treating B cell-mediated autoimmune diseases. Multiple APRIL-targeting therapies including sibeprenlimab, telitacicept, and povetacicept have shown clinical efficacy in reducing proteinuria and pathogenic antibody levels in conditions like IgA nephropathy and systemic lupus erythematosus 678, offering advantages over B cell depletion strategies by preserving memory B cell function.