CTL activity of the CAR T cells was measured using a flow cytometry based assay. CAR T cells and target cells (CII-specific T cell hybridoma) were mixed at a 2:1 effector to target ratio, and CTL lysis measured at 4 and 24 hrs. Despite the expression of exhaustion markers, DR1-CII CAR T cells were active as CTL in the lysis of CD4+ T cells to similar levels from day 20 through day 62 in culture. To measure lysis, cells were labeled with fluorochrome conjugated antibodies specific for TCR-BV8.3 (marker for CII-specific T cell targets), CD8, and DR, and data are based on gates with a minimum of 10,000 cells analyzed. Data are representative of a minimum of 3 different CAR T cell lines.