Despite these encouraging findings, concerns have been raised about the clinical translation of IL-15 armoring due to toxicities observed in trials of recombinant human IL-15, as well as some studies of IL-15-armored CAR T-cells in mice, including cytokine release syndrome (CRS), thrombocytopenia, and liver toxicity (32–36). This evidence concerns the gene IL15 and congenital rubella syndrome.