As CD8+ T cells are known to be the principal antiviral effector cells that control infection after syngeneic HCT in organs (Holtappels et al., 1998; Podlech et al., 1998, 2000), this finding was a first hint to suppose a difference between HvG-HCT and GvH-HCT in the reconstitution and/or tissue recruitment of antiviral CD8+ T cells. The gene discussed is CD8A; the disease is infection.