(A) Overview of in vivo NKT persistence experiments. NSG mice were injected intravenously with CHLA-255 neuroblastoma cells followed 7 days later by luciferase-labeled CAR.GD2 or control NKTs. NKTs were tracked by bioluminescence imaging every two-to-three days. (B) Bioluminescent monitoring of NT, IL-15, GD2.28z, and GD2.28z.15 NKTs injected into groups of mice (n=8/group) carrying CHLA-255 xenografts. Shown are representative results from one of three experiments (each with a separate NKT donor). (C) Quantification of bioluminescence images in B. ***p < 0.001, GD2.28z versus GD2.28z.15, Student’s unpaired t-test. (D) Quantification of NKT cells (human CD45+/NKT+) in total bone marrow cells at day 20 as determined by flow cytometry. *p < 0.05, **p < 0.01, one-way ANOVA. (E) Quantification of neuroblastoma tumor cells (human CD56+/GD2+) in total bone marrow cells at day 20 as determined by flow cytometry. Five mice in both NT and IL-15 groups were granted exceptions to delay euthanasia until day 20, but could not be imaged on day 18. *p < 0.05, **p < 0.01, NS: not significant, Student’s unpaired t-test.