Case report: characterization of autologous BAFF-R CAR T-cell product before infusion and CAR T-cell expansion after infusion in a patient with MCL. Autologous CAR T cells were stimulated with Z138 (BAFF-R⁺ and CD19⁺) target cells or their control Z138 BAFF-R⁻ target cells at an E:T ratio of 1:2 for 5 hours. Bulk stimulated CD4⁺ and CD8⁺ T cells were then enriched and loaded onto microchips for secretomic evaluation. Polyfunctionality was expressed as (A) the percentage of single cells that released >2 cytokines, or as (B) PSI. (C) The WPRE copy number per mL of blood for BAFF-R CAR from the patient with MCL was determined by polymerase chain reaction of genomic DNA extracted from peripheral blood collected at time points from day 0 to day 28 after CAR T-cell infusion.