CD47 and anemia: High CD47 expression on normal cells among which RBCs, platelets and lymphocytes express elevated levels of CD47 led to significant toxicities (mainly thrombocytopenia, anemia, neutropenia and lymphopenia) in the clinical trials with anti-CD47 mAb Hu5F9-G4 (18), which were mitigated by injecting patients with a low-priming mAb dose to occupy the RBC sink and induce compensatory erythropoiesis (19, 20).