However, HEK293T cells, undifferentiated THP-1 cells and activated CD4+ T cells are not refractory to HIV-1 infection despite expressing SAMHD1 [270, 275], suggesting that the antiviral activity of SAMHD1 may be biologically important only in differentiated or non-dividing cells such as DC and macrophages. This evidence concerns the gene CD4 and HIV-1 infection.