IL6 and neoplasm: ,29 Upon tumor cell encounter, CAR-T cells release different pro-inflammatory cytokines, such as TNF-α, IFN-ɣ, IL-1, and granulocyte-macrophage colony-stimulating factor (GM-CSF), that leads to macrophage recruitment and activation, causing a dangerous cytokine storm involving IL-6 and GM-CSF.30