Fig. 5

Changes in CD19 and CD22 cell surface expression in relapsed patient baseline and at the time of relapse. Bone marrow samples were obtained from patients 1 and 2 before cell infusion and at the time of relapse. Mononuclear cells isolated from the bone marrow samples were stained for CD45, CD34, CD19, and CD22. After gating on live cells, the blast gate (CD45+side scatter [SSC] low) was subgated on CD34⁺ cells, and histograms were generated for CD19 and CD22 expression. a CD19 and CD22 expression of B-ALL tumor cells in patient 1 from the initial diagnostic BM sample and the relapsed sample. b CD19 and CD22 expression of B-ALL tumor cells in patient 4 from the initial diagnostic BM sample and the relapsed sample. c Non-transduced (NT) T cells from the leukapheresis product or CAR T cells from the end-of-product formulated cells were incubated with the relapsed B-ALL tumor cells from patients 1, 2, and 4. Effectors were incubated with tumor cells at a 50:1 effector/target ratio for 4 h. Supernatants were harvested and analyzed using the CytoTox 96 Non-Radioactive Cytotoxicity Assay kit (Promega). d Changes in the CD19 cell surface expression in patient 2 between the baseline time point and the time of relapse. e Direct Sanger sequencing performed with patient 2 cDNA. Mutations in exon 2 of CD19 were found in the relapse samples from patient 2 and were predicted to result in a truncated protein. f Emergence of leukemia cell populations with CD22 expression different from that of the cells harvested before treatment. g The change in CD22 cell surface expression in patients 1, 2, and 4