Autologous T cells are genetically engineered to express a chimeric antigen receptor targeting CD19. When the CAR binds CD19 on B-lineage cells, it triggers T-cell activation (CD3zeta with costimulatory signaling), proliferation, cytokine release, and perforin/granzyme-mediated cytotoxicity, leading to depletion of CD19+ B cells and plasmablasts, reduction of autoantibody production, and reset of humoral immunity.