B-cell reconstitution following HSCT and CD19 CAR T–cell infusion. PBMCs from patient blood were analyzed by flow cytometry at different time points after adoptive transfer. (A) Samples were analyzed by multiflow cytometry after staining with 7-AAD, CD3 VioBlue, CD19 PE, CD20 FITC, and CD10 APC for the analysis of B-cell reconstitution. Absolute CD19⁺ cells were calculated based on the percentage of CD19⁺ cells, white blood cell counts, and percentage of lymphocytes. (B) Rituximab levels in the serum of the patients were determined with a time-resolved fluorometry assay.