IL6 and congenital rubella syndrome: Furthermore, in leukaemias, studies of Norelli M et al. using xenotolerant murine models and Giavridis T et al. in SCID-beige mice showed that CRS was associated with an increase in IL-1 and IL-6, a hallmark of CRS, and that the monocytes and not CAR T cells were the major source of both cytokines in CRS [120,121].