TACI, transmembrane activator and CAML-interactor, is a member of the TNF receptor superfamily (TNFRSF). Within the TNFRSF, it shares the highest homology with BCMA. TACI and BCMA both bind APRIL and BLyS/BAFF, members of the TNF superfamily. TACI is expressed on the cell surface of B cells and activated, but not resting, T cells. Human and mouse TACI share 54% amino acid sequence identity.