CTLA4 and B-cell chronic lymphocytic leukemia: Trans-costimulation enhanced CAR-ROR1 T-cell proliferation (Supplementary Fig. S3B) and the activation phenotype of both CAR-ROR1 and CAR19 T cells as assessed by PD-1, TIM-3, and CTLA-4 upregulation in CLL cocultures (Supplementary Fig. S3C–S3E).