Selective targeting of patient’s CLL cells in the presence of healthy B cells by anti-FcµR CAR T cells. (A) Peripheral blood lymphocytes (0.5 × 10⁶ cells) from a CLL patient were stained with the APC-conjugated anti-CD5 mAb and the PE-conjugated anti-CD19 mAb. The cell populations (CD19⁺ CD5⁻ non-CLL B cells, CD19⁻CD5⁺ T cells, CD19⁺ CD5⁺ CLL cells) were recorded for FcµR using the FITC-conjugated anti-FcµR mAb 6B10 (black line). An isotype-matched control antibody served as control (gray histogram). Histograms exemplarily show FcµR levels of each subpopulation. (B) T cells with and without anti-FcμR CAR and anti-CD19 CAR, respectively, were coincubated with PBMCs from a CLL patient (10⁵ cells) in an effector-to-CLL cell ratio of 5:1 for 24 hours. Cells were stained with the FITC-conjugated anti-CD5 mAb and the PE-conjugated anti-CD19 mAb. The number of CD19⁺ CD5⁺ CLL cells and CD19⁺ CD5⁻ healthy B cells in the same patient sample was recorded by flow cytometry. Bars represent the cell numbers; data represent the mean of triplicates ± SD. Statistical analysis was performed using the Student t test (*P < .05; ***P < .001; ns, not significant).