CD4 and infection: By inducing the down-regulation of CD47 from the surface of infected CD4+ T cells, a ligand of the inhibitory “don’t eat me” receptor signal regulatory protein-alpha (SIRPα) expressed on myeloid cells, Vpu thus promotes the phagocytosis of infected T cells by macrophages, leading to productive infection of these target cells by CCR5-using M-tropic viruses and also by non-M T/F viruses [135].