Function of T cells expressing mbaIL6 and anti-CD19 CAR cocultured with a monocytic cell line. (A) Cytotoxicity of T cells against OP-1-mCherry cells, with or without undifferentiated THP-1 cells (1:5:1 T-cell:OP-1:THP-1 ratio). OP-1 growth was quantitated by using the IncuCyte Live Imaging System; results are expressed as mean (±SD) of red calibrated units (RCU) × μm²/well in triplicate measurements. (B) IL-6 levels in the supernatant of the cultures shown in panel A after 48 hours, measured by using ELISA. CAR expression was 84% to 97% for CAR alone and 86% to 96% for CAR plus mbaIL6 (“DUAL”). Mean (±SD) of 3 measurements each with T cells from 2 donors. Not significant (n.s.), P > .05; ****P < .0001. (C) Supernatant from CAR-T/OP-1 48-hour cocultures was added to T cells mixed at 1:1 with either undifferentiated or differentiated THP-1 cells (supplemental Figure 6D). Cytokine levels were measured after an additional 72 hours of culture. Results with T cells transduced with GFP only or mbaIL6 are shown in supplemental Figure 6E.