FLT3LG and graft versus host disease: Five out of the six surviving NRG-HIS/Flt3LG mice, but none of the NRGF-HIS/Flt3L mice, developed significant graft versus host disease (GVHD) by day 20 following infection (Supplementary Figure 6b), which was likely due to the priming of allogeneic T cell responses by the Flt3LG-expanded murine DCs activated by YFV-17D.