Infectious or AT-2 HIV induces IDO mRNA expression and enzymatic activity in PBMCs of HIV-uninfected donors. (A) IDO mRNA was measured by quantitative real-time PCR in PBMCs from HIV-uninfected donors cultured for 24 hours in presence of MVs, AT-2 HIV_MN, AT-2 HIV_Ada, infectious HIV_MN, and infectious HIV_Ada (solid bars); a series of experiments was performed using CTLA-4-Fc and CD28-Fc (open bars); mean values (n = 6) ± SE are shown. (B) Ratios between the concentration of kynurenine (μM) and tryptophan (mM) were measured by HPLC in supernatants from PBMCs cultured with microvesicles (control), AT-2 HIV, or AT-2 HIV and 1-mT for 24 and 48 hours; mean values (n = 5) ± SE are shown.