Changes in circulating cytokine levels including IL15 were similar in CAR and 15.CAR cohorts (Extended data fig 4A, B), and patients with CRS had increased concentrations of IFNγ, CCL2, TNFα, eotaxin, IL6, CXCL10, MIP1β, and IL15 (Extended data fig S4C and D). Here, IL6 is linked to congenital rubella syndrome.