Autologous T cells are genetically engineered to express chimeric antigen receptors that bind CD19, CD20, and BCMA on malignant B-lineage cells. Antigen engagement activates CAR signaling (CD3ζ with co‑stimulatory domains), driving T‑cell activation, proliferation, cytokine release, and perforin/granzyme-mediated cytotoxic killing of target cells. Multi-antigen targeting reduces antigen escape, and prior lymphodepletion supports in vivo expansion and persistence.