qPCR analysis of SIV-gag showed that the MDSCs were infected by SIVmac251 in vivo.

<p>(A) Sorting strategies for MDSCs and CD4⁺T cells from the PBMCs of SIV-infected macaques. (B) The ratio of mRNA of SIVgag vs mRNA of CD4 in CD4⁺T cells and MDSCs showed that MDSCs had a higher SIVgag/CD4 ratio. (C) The ratio of SIVgag expression level in MDSCs vs SIV gag expression level in CD4⁺T cells showed that MDSCs and CD4⁺T cells had a comparable level of SIVgag expression. (D) In another independent experiment, MDSCs and CD4⁺ T cells from the PBMCs of the SIV-infected animals were sorted as in A. For the sorted CD4⁺ T cells, the samples were serially diluted (10–fold) before the RNA isolation. After RNA isolation and cDNA synthesis, each of the CD4⁺ T and MDSC samples was subjected to qPCR analysis for SIVgag, CD3, CD4, and GAPDH using the same amounts of cDNA. The detection limit for Gag and CD4 is 50 copies/well (shown by the dashed horizontal lines). If the gag copy number was lower than 50, 50 was assigned to the tested sample. Black dots in D are CD4⁺ T cells as positive control titration curve, while red squares are the MDSCs plotted on the same scale, and red numbers are the copy numbers of SIVgag in MDSCs. The number of cell equivalents used in each assay was shown in the horizontal axis.