IL2 and neoplasm: CRS is characterised by the rapid release of pro-inflammatory cytokines (IFNγ, TNFα, IL-2 and GM-CSF) from activated CAR-Ts (especially 4th generation TRUCK CAR-Ts) and tumour cells, which initiate hyperactivation of immune cells such as Mφs, DCs and NKs resulting in mass cytokine secretion (IL-1β, IL-5, IL-6, IL-8, IL-10, IFNγ, TNFα, MCP-1, MIP-1β and GM-CSF) into the peripheral circulation; eliciting a systemic inflammatory response similar to that in sepsis.