CD28 and congenital rubella syndrome: The CD28 costimulatory domain results in rapid T-cell expansion, which leads to an earlier and more severe cytokine release syndrome (CRS), while the use of the 4-1BB costimulatory domain results in a slower expansion of T-cells, as well as a lower incidence and severity of both CRS and immune effector cell-associated neurotoxicity syndrome (ICANS).