One arm targets a tumor-associated antigen expressed on myeloma cells, such as B cell maturation antigen (BCMA), G-protein-coupled receptor class C group 5 member D (GPRC5D), or Fc receptor homolog 5 (FcRH5), while the other binds the CD3ε subunit of the T cell receptor (TCR) complex on cytotoxic T lymphocytes. The gene discussed is TNFRSF17; the disease is plasma cell myeloma.