We demonstrate that BCMA clone 4C8A binds with high affinity to the whole BCMA extracellular domain (amino acids 1–54 a.a), but not to a fragment of BCMA consisting of residues 3–17 a.a. We initially generated monoclonal antibodies against this fragment, but the antibodies did not exhibit sufficient specificity for multiple myeloma cells. This evidence concerns the gene TNFRSF17 and plasma cell myeloma.