This is partly due to a differential cytokine secretion profile, for example, activated NK cells usually produce IFN-γ and GM-CSF [197] whereas CAR-T cells predominantly produce IL-1, IL-6, Tumor Necrosis Factor-α (TNF-α) or Monocyte Chemoattractant Protein-1 (MCP-1), all which are associated with CRS and severe neurotoxicity [198]. Here, IL6 is linked to congenital rubella syndrome.