KIT and infection: Importantly, infection of IkNULL lin− HPCs with pMSCV/Ik1 increased c-Kit expression to 74% and Flt3 expression to 46.7% (if their expression levels in IkWT/GFP lin− HPCs is considered as 100%), whereas expression of c-Kit and Flt3 genes was only increased to 33.3% (for c-Kit) and 11.5% (for Flt3) upon pMSCV/Ik1ΔPP1 infection (Figure 5B).