Multiple cytokines are elevated after CAR-T cell infusion, such as interferon-gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), granulocyte–macrophage colony-stimulating factor (GM-CSF), and interleukin 6 (IL-6), but cytokine levels are not always correlated with CRS severity, and their timely monitoring is challenging [5, 39, 41–45]. This evidence concerns the gene IL6 and congenital rubella syndrome.