CD4 and AIDS: Moreover, in non-human primates (NHPs) infected with simian immunodeficiency virus (SIV), blocking the IFNα/β receptor (IFNAR) via an IFN-I receptor antagonist increased blood SIV reservoir size, decreased the number of proliferating Ki67+ CD4+ T cells, and accelerated CD4+ T cell depletion and progression to acquired immunodeficiency syndrome (AIDS).