TNFRSF17 and AL amyloidosis: 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.