18 A STAT-5 phosphorylation assay was used to gauge IL-7 responsiveness in CD4+ and CD8+ cells. The increase of the percentage of P-STAT-5 cells, and an example of constitutive P-STAT-5 and IL-7-induced P-STAT-5, in HD and NHP are shown in Fig. 5(a,b). In NHPs, (n = 15) 84·4 ± 10·8% and 60·6 ± 12% of CD4+ and CD8+ cells showed an increase of P-STAT-5 cells in response to IL-7 stimulation. Similar numbers were obtained in PBMCs from HDs (n = 10): 87·6 ± 7·6% and 62·3 ± 15·4% in CD4+ and Opaganib concentration CD8+

cells, respectively. CD4+ and CD8+ subsets showed comparable responses to IL-7 stimulation as measured by STAT-5 phosphorylation in NHPs and HDs. In HDs and NHPs more CD4+ cells than CD8+ cells showed STAT-5 phosphorylation (consistent with higher levels of IL-7Rα expression on CD4+ T cells) but the amplitude (measured by MFI) was not statistically different between CD4+ and CD8+ cells. The presence of regulatory cells was assessed by expression analysis of CD25 and FoxP3 in the CD4+, CD8+ and CD4+ CD8+ T-cell compartments (gating strategy see Supplementary Fig. S2). In NHPs, the

CD4+ T-cell compartment showed the following frequencies: 16·5% (median values) were CD25intermediate (CD25interm.) and 0·5% stained for CD25bright; in CD4+ CD8+ T cells: 19·6% cells were CD25interm. and 1·4% were CD25bright; in CD8+ T cells: 1% were CD25interm. and 0·07% CD25bright (Table 2). Compared with HDs, higher frequencies of CD4+ CD25interm. T cells and CD4+ CD8+ CD25interm./bright,

and CD8+ CD25bright T cells (21%) were detected in PBMCs from NHPs. Analysis RAD001 concentration of FoxP3 expression in the different CD25+/− T-cell compartments showed that the majority of CD25bright T cells in NHPs were FoxP3+ (87·5% of CD4+ and 76% of CD4+ CD8+ and CD8+ T cells), whereas ADP ribosylation factor only 10–20% of CD25interm. T cells showed FoxP3 expression (Fig. 6a). In contrast, almost no FoxP3 expression could be observed in human CD4+ CD8+ CD8+ T cells that exhibited the CD25interm. phenotype. Analysis of PBMCs from four of eight HDs showed that CD4+ CD8+ and CD8+ T cells, which displayed a CD25bright phenotype, stained also positive for FoxP3. In summary, statistically higher frequencies (P ≤ 0·05) of CD4+/− CD25interm.FoxP3+/−, CD4± CD8± CD25interm./high FoxP3+/− and CD8± CD25interm./high FoxP3+/− were detected in NHPs than in HDs. Expression of the IL-7Rα on NHP CD25bright T cells was inversely correlated with expression of FoxP3, which is similar to the situation described in humans.25 More than 90% of NHP CD4+ CD8+ CD25interm./bright FoxP3+ T-cell subsets did not express the IL-7Rα, whereas the majority of CD4+ CD8+ CD25+/− FoxP3− (33–67%) were positive for IL-7Rα (% of IL-7Rα expression is shown for CD4+ T cells in Fig. 6b). The same trend was observed in HDs. However, 9% of human CD4+ CD25bright FoxP3+ T cells expressed the IL-7Rα (Fig. 6b), this was not true for the same T-cell subset in NHPs (3·8%).