For example, in renal transplant recipients suffering from HCMV-induced disease, the HCMV-specific memory CD4 T cell response was found to be diminished compared to asymptomatic infections [21] and in stem cell transplant recipients an increased level of IFN-γ secreting HCMV-specific CD4 T cells was associated with a drop of virus load [22]. This evidence concerns the gene CD4 and infection.