Autologous genetically engineered T cells expressing an anti-CD19 chimeric antigen receptor; administered as a single IV infusion with 3+3 dose escalation (1×10^5, 3×10^5, 1×10^6 CAR+ cells/kg) after lymphodepletion. The CAR redirects patient T cells to recognize CD19 on B cells, triggering T-cell activation, proliferation, cytokine release, and perforin/granzyme-mediated cytotoxic killing, with expected on-target B-cell depletion.