Our conclusion is further supported by the observation that currently available preclinical xenograft mouse models are poorly predictive of the clinical toxicity of CAR T cells owing to the lack of bystander human hematopoiesis and therefore lack of CRS development (monocytes rather than CAR T cells are primarily responsible for the systemic release of IL-6 which ultimately causes CRS). The gene discussed is IL6; the disease is congenital rubella syndrome.