CD19 and osteosarcoma: Of the two osteosarcoma models, one osteosarcoma model clears efficiently and is associated with minimal cytokine release with CAR T cell therapy (henceforth referred to as “rapid-clearing osteosarcoma”), and one osteosarcoma model is more aggressive, is engineered to express CD19 for experimental CAR T cell studies, and is associated with high cytokine release with CAR T cell therapy (henceforth referred to as “aggressive osteosarcoma”)23,24.