CD19 and B-cell chronic lymphocytic leukemia: From the total lymphocyte count multiplied by the CD19+ lymphocyte fraction and the clonotype burden from the targeted sequencing of IGH rearrangements, an estimate of the CLL cell counts prior to ibrutinib or R–v treatment was calculated to be 26.6 × 109/L (Figure 1C, 25% percentile: 6.5 × 109/L, 75% percentile: 44.5 × 109/L), dropping to 0.6 × 109/L for ibrutinib and close to the detection limit for R–v (Figure 1C, insert).