To investigate the role of AHR in HIV-1 infection, the endogenously expressed AHR in HEK293 T cells, Magi/CCR5 (Fig. 3C), and PHA-P-activated primary CD4+ T cells (Fig. 3E, left panel) was knocked down by using specific small interfering RNAs (siRNAs) or lentiviruses containing AHR-specific shRNAs, and then cells were infected with pseudotyped HIV-1. Here, CD4 is linked to HIV-1 infection.