T_H17 cells programmed with an ICOS-based CAR show enhanced persistence that is dependent on antigen encounter. (A) NSG mice from the experiment shown in Figure 6, which were treated with intratumoral injections of redirected T_H17 /T_C17 cells, were killed on day 51 after T-cell infusion. Peripheral blood was quantified for the presence of human CD4⁺ and CD8⁺ T cells by a FACS Trucount assay. Results are expressed as a mean absolute T-cell count per μL of peripheral blood ± SD (n = 9 for all groups). Representative of 2 different experiments. (B-C) Redirected T cells were obtained from mouse spleens on day 51 after treatment. The number of CD4⁺ and CD8⁺ T cells (B) and the percentage of CD161⁺ CAR⁺ CD4⁺ T cells (C) were analyzed by flow cytometry. Error bars represent SD. (D) Human L55 non–small cell lung cancers were established in the flanks of NSG mice. After 3 weeks, when the tumors reached a volume of 150 mm³, mice without tumors (empty mice) or with preestablished tumors were treated with 2 IV injections of 10 × 10⁶ T_H17 /T_C17 cells. The concentration of CD4⁺ T cells was determined in the blood of treated animals 3 weeks postinfusion. *P < .05, **P < .01, and ***P < .001. Representative of 1 experiment.