Autologous T cells are genetically engineered to express a second‑generation anti‑CD19 chimeric antigen receptor with CD3ζ signaling plus a costimulatory domain. Upon binding CD19 on B‑cell malignancies, the CAR triggers T‑cell activation, expansion, cytokine release, and cytotoxic killing of CD19‑positive cells, often resulting in depletion of normal B cells (B‑cell aplasia).