Several factors determine the occurrence and intensity of (CRS), hemophagocytic lymphohistiocytosis (HLH), macrophage activation syndrome-like activation (MAS-L) (HLH/MASL), and immune effector cell-associated neurotoxicity syndrome (ICANS), including tumor type, specific target, and CAR design (Roex et al., 2020). Here, MAS1L is linked to hemophagocytic syndrome.