Preexisting and posttreatment anti-mCAR19 antibodies vs tisagenlecleucel expansion. Tisagenlecleucel expansion (C_max) in pediatric and young adult patients with r/r B-ALL by preexisting (baseline) (A) and posttreatment (postinfusion) (C) anti-mCAR19 antibodies. Patients in the ELIANA trial are indicated by blue circles, and patients in the ENSIGN trial are indicated by red triangles. Tisagenlecleucel expansion (C_max) in adult patients with r/r DLBCL by preexisting (baseline) (B) and posttreatment (postinfusion) (D) anti-mCAR19 antibodies. Patients in the JULIET trial are indicated by blue diamonds.