Development of ABO titer (blue, left axis) and reticulocytes (red, right axis) related to the number of daratumumab administrations. Reticulocytosis was defined as reticulocyte count of 25 × 10⁹/L. Please refer to supplemental Figure 1 for the development of ABO titer in all patients. • = occurrence of reticulocytosis, n = total number of given daratumumab treatments.