To evaluate whether FIX generated in vivo by LV-FIX gene therapy inhibits the activation or even deplete FIX-specific BMEM, we measured the frequency of FIX-specific BMEM (CD19+B220+IgM−IgD−) in LNs harvested from inhibitors-positive haemophilia B mice after LV-FIX gene therapy (Fig 5C,D). This evidence concerns the gene CD19 and hemophilia.