Fig. 5. The CD47-targeting safety strategy for HIP CAR T cells.

a, b HIP CAR T cells were challenged with NK cells (a) or macrophages (b) in the presence and absence of SIRPα-Fc IgG1 or IgG4, or a SIRPα with poly-His tail (upper rows, three independent replicates per group and time point). Effector cell Fc was blocked by Fc block solution (lower rows, three independent replicates per group and time point in one experiment). c Immunodeficient NSG mice were injected with 1 × 10⁶ Luc⁺ Nalm6 cells and received 3 × 10⁶ HIP CAR T cells or Mock T cells on day 3. In two HIP CAR T groups, mice additionally received three doses of the SIRPα-Fc IgG1 or IgG4 on days 3, 4, 5, and 8. Spleen and bone marrow were taken after 27 days. d BLI images show the tumor burden for all mice in this study. e Graphs show BLI signals for animals receiving HIP CAR T cell with or without the SIRPα-Fc IgG1 or IgG4 (mean ± SEM, n = 5 animals per group in one experiment, arrows indicate SIRPα-Fc i.v. injections). f, g The percentage of CAR⁺ cells in the bone marrow (f) and spleen (g) were assessed on day 27 (mean ± SD, n = 5 animals per group). No HIP CAR T cells were detected in animals that received either fusion protein (ANOVA with Bonferroni’s post hoc test). h The percentage of CD19⁺ cells in the bone marrow was assessed on day 27 (mean ± SD, n = 5 animals per group). There were no differences between the animals receiving Mock T cells or HIP CAR T cells with either fusion protein (ANOVA with Bonferroni’s post hoc test).