CD19 and neoplasm: As cellular products, CARTs do not exhibit typical pharmacokinetic properties of traditional drugs and the unique biology of CARTs explains the specific toxicities associated with this therapy including cytokine release syndrome (CRS), neurotoxicity, cytopenia, on-target-off tumor effects (i.e., B cell aplasia and consecutive hypogammaglobulinemia in CD19 CART therapy) and infections.