CD28 and neuroblastoma: We observed a 3.2-fold increase in L1CAM-4-1BB CAR T cell-induced cytotoxicity and a 1.5-fold increase in the L1CAM-CD28 CAR T cell-induced cytotoxicity against neuroblastoma cells expressing intermediate levels of the target antigen (IMR-5/75) compared to CAR T cell treatment alone.