IL2 and congenital rubella syndrome: Cytokine release syndrome (CRS) is a potentially life‐threatening toxic effect of immunotherapy and was first described after treatment with blinatumomab4 or with chimeric antigen receptor (CAR)‐modified T cells.5, 6 CRS results from the activation and cytotoxic‐mediated damage of monocytes, macrophages, and different lymphocyte populations with a massive release of inflammatory cytokines, including IL‐6, IFNγ, and IL‐2.