CD19 and acute lymphoblastic leukemia: IGRT was administered to 35 of 65 participants (54%) within 16 weeks (≥4 half-lives of IgG) (21) before sample collection and was more frequent in CD19-CAR-T cell recipients younger than 18 years old, BCMA-CAR-T cell recipients, participants with ALL, and participants with a prior allogeneic HCT (Table 1).