A profound eradication of CLL cells from the bone marrow and blood occurred after infusion of anti-CD19-CAR T cells into patient 1. (A) A bone marrow biopsy was performed 2 days before anti-CD19-CAR T cells were infused. Bone marrow immunohistochemistry staining showed that 80% to 90% of the bone marrow cells consisted of atypical lymphoid cells that had a morphology consistent with CLL. The atypical lymphoid cells were CD79a⁺ and CD19⁺. Flow cytometry staining for immunoglobulin light chain restriction showed that the cells were clonal (not shown). (B) Twenty-six days after the anti-CD19-CAR T-cell infusion, immunohistochemistry staining of a bone marrow specimen showed no morphologic evidence of CLL. Only rare CD79a⁺ cells were present. (C) Blood B cells, of which 99% were CLL cells, dropped dramatically after infusion of anti-CD19-CAR T cells. (D) Patient 1 was dependent on platelet transfusions before the infusion of anti-CD19-CAR T cells. After the CAR T-cell infusion, the patient no longer required platelet transfusions. His platelet count increased for ∼2 months after the anti-CD19-CAR T-cell infusion; subsequently, his platelet count decreased when his CLL progressed.