TNFRSF13B and neoplasm: APRIL also binds TACI, a tumor necrosis factor receptor that has a role in the maturation of B cells, with increased expression on maturing B-cell stages compared with BCMA.34 35 TACI was initially thought to be a T-cell antigen36 but now accepted to be expressed primarily on B cells21 with a recent report suggesting expression in suppressive T-cells.37 Importantly, TACI is expressed on MM cells.5 We found BCMA and TACI to be coexpressed on tumor for the majority (78%) of patients, but at generally lower levels than BCMA (median BCMA 1061 ABC, median TACI 333 ABC).