APRIL

APRIL, a proliferation-inducing ligand, is predominantly produced by myeloid cells—including dendritic cells, monocytes, neutrophils, and macrophages—and to a lesser extent by activated B cells. It binds to TACI, BCMA, and HSPG receptors, modulating B-cell activation, plasma cell survival, and immunoglobulin class switching. This protein plays a role in B cell maturation, class-switch recombination, and the formation of long-lived plasma cells. APRIL is also implicated in autoimmune diseases such as systemic lupus erythematosus and IgA nephropathy, as well as in various cancers, including breast, colorectal, and non-small cell lung cancer. Its abnormal expression is associated with tumor cell proliferation, survival, and invasion, making it a potential therapeutic target.