Cytokine release syndrome (CRS)/Cytokine storm: (a) cytokines are proteins that immune cells release when they attack an infection. The rapid and massive release of cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interferon-γ (IFN-γ) into the bloodstream of patients can lead to fever, chills, hypotension, tachycardia, trouble breathing, and low oxygen. (b) CRS is considered an "on-target" effect of CAR-T cell therapy—as its presence shows that the T cells are in action, releasing the cytokines that stimulate the immune response against tumor cells. Here, IL6 is linked to congenital rubella syndrome.