Prolonged B-cell depletion after anti–CD19-CAR-transduced T-cell infusion. (A) Immunohistochemistry staining of a pretreatment bone marrow biopsy shows a large population of CD79a⁺ cells. (B) Thirty-six weeks after anti–CD19-CAR-transduced T-cell infusion, rare CD79a⁺ cells were detected by immunohistochemisty staining of a bone marrow biopsy. The cells did not appear to be plasma cells morphologically. The number of CD79a⁺ cells was substantially below normal limits. The arrow indicates one of the rare CD79a⁺ cells. (C) The blood B-cell count of the patient treated with anti–CD19-CAR-transduced T cells is shown before treatment and at multiple time points after treatment. B cells were measured by flow cytometry for CD19. The dashed line indicates the lower limit of normal. Day 0 is the day of the second anti–CD19-CAR-transduced T-cell infusion. (D) The mean ± SEM blood B-cell count is shown for patients who received infusions of T cells targeted to either the NY-ESO antigen or the gp100 antigen. The patients all received the same chemotherapy and IL-2 regimen as the patient who received anti–CD19-CAR-transduced T cells. NY-ESO and gp100 are not expressed by B cells. Day 0 is the day of T-cell infusion. All available B-cell counts were included for each time point (pretreatment, n = 28; 4-5 weeks after T-cell infusion, n = 29; 8-11 weeks after T-cell infusion, n = 31; 14-19 weeks after T-cell infusion, n = 20). All patients with available samples had a B-cell count in the normal range by 14 to 19 weeks after T-cell infusion. (E) The blood CD3⁺ T-cell count of the patient treated with anti–CD19-CAR-transduced T cells is shown before treatment and at multiple time points after treatment. (F) The blood NK cell count of the patient treated with anti–CD19-CAR-transduced T cells is shown before treatment and at multiple time points after treatment. NK cells were measured by flow cytometry as CD3⁻, CD16⁺, CD56⁺ cells. (E-F) Day 0 is the day of the second anti–CD19-CAR-transduced T-cell infusion, and the dashed line indicates the lower limit of normal. (G) The serum IgG level of the patient treated with anti–CD19-CAR-transduced T cells is shown before treatment and at multiple time points after treatment. Day 0 is the day of the second anti–CD19-CAR-transduced T-cell infusion. (H) Real-time polymerase chain reaction was performed with a primer and probe set that was specific for the anti-CD19 CAR. Anti–CD19-CAR-transduced T cells were undetectable in pretreatment blood samples. The anti–CD19 CAR transgene was detected in the peripheral blood of the patient who received anti–CD19-CAR-transduced T cells from 1 to 27 weeks after anti–CD19-CAR-transduced T-cell infusion.