APRIL - a type II transmembrane protein [250 aa, cytoplasmatic domain: 28aa, transmembrane domain: 21aa, extracellular domain: 201aa] is considered to be involved in autoimmune and cancer diseases. It stimulates proliferation of tumor cell lines and seems to play a role in tumorgenesis. In general it is involved in B and T cell proliferation, triggers humoral immune responses, activates NF-κB and induces cell death.TACI (transmembrane activator) and BCMA (B-cell maturation antigen) are considered to be receptors for APRIL. APRIL belongs to the TNF-Superfamily which is involved in immune responses and apoptosis.