(a) Representative flow cytometric profiles showing the typical frequencies (%) of PD-1/CD200-defined subsets within the (CD95high) CD4+ memory T cell populations in LNs of SIV-, elite controller (EC), semi-controller (Semi), progressor (Prog) and cART-suppressed SIV-infected (cART) monkeys (see ). (b) Relative frequencies of CD4+ TFH (CD200high/PD-1high) within the total CD4+ memory T cell populations in LN of the designated monkey groups (black bars indicate the median value for each group). The Kruskal-Wallis test was used to determine the significance of overall differences in %CD4+ TFH among these monkey groups (p value shown), and if this p value was <0.05, the Wilcoxon rank-sum test was used to perform pair-wise analysis (brackets indicate p<0.05). (c,d) Detection of replication-competent SIVmac239 from sorted PD-1/CD200-defined CD4+ memory T cell subsets of LNs from semi-controller and EC monkeys after 13 days of CEMx174 cell co-culture with 105 sorted LN cells, and from progressor monkeys after 17 days of CEMx174 cell co-culture with 104 sorted LN cells (note: fewer sorted CD4+ memory T cells were available in progressor monkeys due to CD4+ T cell depletion). Representative results are shown in (c), with plasma viral load (in SIV RNA copies/ml) at the time of biopsy shown in parenthesis under the monkey identification numbers, and all analyses are shown in (d) with light colored lines delineating individual monkeys and bold diamond symbols delineating log median values of each group. The Friedman test was used to determine the significance of overall differences in detection of replication-competent SIV among the PD-1/CD200-defined CD4+ memory T cell subsets (p values shown), and the Wilcoxon signed-rank test was used to perform pair-wise analysis when the Friedman p value was <0.05 (brackets indicate Wilcoxon signed-rank p<0.05). (e,f) Comparison of cell-associated SIV RNA (e) and DNA (f) levels in the same LN CD4+ memory T cell subsets, with statistical analysis as described in (d).