In patients receiving 4-1BB costimulated CD19-CAR T cells, elevations in IFN-γ, IL-6, IL-8, sIL-2R, sgp130, MCP1, MIP1α, MIP1β, and GM-CSF as well as higher ferritin (>10,000) and CRP were significantly associated with severe (Grade 4-5) CRS compared to those with mild (Grade 0-3) CRS (96). This evidence concerns the gene IL6 and congenital rubella syndrome.