Frequency of R5 and X4 HIV-1 infection in blood and thymic DC. (A) Plasmacytoid DC (pDC) and myeloid DC (mDC) were isolated from blood and thymus tissue. Cells were exposed to either R5 (NL(AD8)-nef/EGFP) or X4 HIV-1 (NL4-3-nef/EGFP). The number of EGFP+ cells was determined by flow cytometry 5 days post-infection. Each symbol represents the mean of duplicate experiments from a single donor. The edges of the boxes represent the 25 and 75 percentiles, the horizontal line in the box is the median and the whiskers extend to the minimum and maximum data points. * indicates a p value of < 0.05 as determined by the Wilcoxon signed rank test. (B) In some experiments the DC were pre-treated with AZT (0.1 μM) prior to infection. Representative results form 4 experiments are shown. (C) DC viability was assessed by flow cytometry following 5 days of culture and expressed as a proportion of live cells over total cells. Each column represents the mean of 5-6 experiments ± SEM.