CD4 and HIV-1 infection: Although iDCs express receptors and co-receptors required for HIV-1 infection (Granelli-Piperno et al., 1996; Turville et al., 2002), their infection rates in culture are lower than the ones for activated CD4+ T cells or macrophages (Cameron et al., 1992a; Granelli-Piperno et al., 1998; Granelli-Piperno et al., 1999; Pope et al., 1995).