CD53 and plasma cell myeloma: Monoclonal antibodies against the cell surface antigen CD38, e.g., isatuximab, daratumumab, or Mor202, have entered the therapeutic armamentarium in multiple myeloma due to single agent overall response rates of 29 vs. 36 vs. 31%, respectively, effectivity in combination regimen, e.g., with lenalidomide or bortezomib plus dexamethasone, and tolerable side effects (1–6).