CD4 and HIV infectious disease: The impact of Treg on HIV infection is controversial with some studies suggesting that Treg exert a beneficial effect by limiting autoimmunity, HIV replication and CD4+ T-cell depletion17, 18, 24, 25, whereas others suggest that Treg have a detrimental effect by inhibiting HIV-specific immune responses and causing disease progression20, 21, 28, 29.