In this recent report, a range of methodologies have been used to document the glycan difference between rFVIII products and the subsequent effects on the FVIII immune response in vitro and in both “regular” (fully murine) F8-KO HA mice (F8 exon-16 deletion) and in humanized hemophilic mice expressing a mutant human F8 transgene product (with the hemophilia-causing mutation FVIII-Arg593Cys). The gene discussed is F8; the disease is hemophilia.