mDC and pDC frequencies are significantly reduced during HIV infection. (A) The percentages of mDCs and pDCs were calculated based on the following gating scheme. Total viable PBMCs were gated based on their forward and side scatter (left panel). After 4-color staining with anti-lineage (CD3, CD14, CD16, CD20, and CD56) and anti-HLA-DR antibodies, mDCs and pDCs were identified as lineage negative and HLA-DR positive cells (middle panel). Additionally, pDCs expressed CD123 (right top panel), while mDCs expressed CD11c (right bottom panel). The percentages of (B) mDCs and (C) pDCs within PBMCs in the following groups of subjects are shown: U, uninfected; HR, high risk; primary infection: Fiebig stages I-II (N = 11), III-IV (N = 3), and V-VI (N = 27); E, early established infection (N = 6); CU, chronic/untreated (N = 9); CT, chronic/treated (N = 9); LTNP, long-term nonprogressor (N = 8); and EC, elite controller (N = 6). Horizontal bars indicate the median values. Hollow dots represent outliers. The nonparametric Mann-Whitney U test was used to determine whether there were significant differences between subject groups in circulating DC frequencies and the results are summarized in the left panels. As indicated, DC frequencies in the HIV seronegative subjects (U plus HR groups) were significantly lower than those in all the HIV-infected subjects. The asterisks indicate P values: ***P < .001, **P < .01, and *P < .05; NS = not significant.