The B cell maturation protein (BCMA) is a type I integral membrane protein that belongs to the tumor necrosis factor receptor (TNF-R) superfamily. It is expressed as a 184 amino acid peptide that is expressed only in mature B-lymphocytes and is located on the cis part of the Golgi apparatus. BCMA shares significant homology with TACI (transmembrane activator) within the cysteine-rich domain. TACI has been shown to bind CAML, which induces activation of NFAT (nuclear factor of activated T cells). Both BCMA and TACI have been shown to bind APRIL and TALL-1, which stimulate B cell proliferation in conjunction with other B-cell activators. When overexpressed, TALL-1 stimulates the development of systemic lupus erythaematosus (SLE).