As infected IFN-γ-KO mice show a more complete HLH spectrum when compared to infected WT BALB/c mice, and as infected WT C57BL/6 mice display little to no HLH-like symptoms [13], this raised the question whether inordinate replication of MCMV, a cytolytic virus, could be the main cause of the observed HLH-like syndrome. This evidence concerns the gene IFNG and hemophagocytic syndrome.