Long-term proliferation and cytokine production of MM CARTs. (A-B) Growth curves of thawed UTDs and BCMA, APRIL, and TriPRIL CARTs in vitro during repeated antigen stimulation (arrows) with irradiated K562 cells expressing either BCMA (A) or TACI (B). Results are displayed as mean population doublings ± SEM of 3 normal donors. (C) Levels of cytokines in supernatants of UTDs, and BCMA, APRIL, and TriPRIL CARTs after overnight coculture with human MM.1S myeloma cells at a 1:1 E:T ratio. Cytokines were measured by 12-plex Luminex assay in technical duplicates. Bars show the mean ± SEM of 3 normal donors. (D-E) Single-cell cytokine profiles of UTDs and BCMA, APRIL, and TriPRIL CARTs stimulated with BCMA- and TACI-expressing target cells captured by 32-plex antibody barcoded chip. Percentage of polyfunctional (≥2 cytokines) CD4⁺ and CD8⁺ T cells (D) and protein secretion of CD4⁺ and CD8⁺ T cells (E) across functional groups (effector, stimulatory, chemoattractive, regulatory, and inflammatory, as indicated). Bars show the mean ± SEM of 3 normal donors. ns, P ≥ .05; *P < .05 **P < .01; ***P < .001 by 2-way analysis of variance (ANOVA).