7 Cytolytic CD56dim CD16+ NK cells comprise 90% of circulatory NK cells, whereas, cytokine-producing CD56bright CD16−/dim NK cells represent about 10%. Examining Ku-0059436 molecular weight the CD56 and CD16 expression patterns of macaque CD8α− NK cells, we found that these cells could be divided into four subpopulations (Fig. 2d): double-negative cells (CD56− C16−) accounted for 22·2 ± 10·6%, 34·2 ± 15·9% of cells were CD56dim CD16+, and CD56dim/+ CD16− cells together represented approximately 39·4 ± 19·3% of CD8α− NK cells. On the other hand,
90 ± 7·9% of CD8α+ NK cells were CD56dim CD16+, but only two other minor populations could be detected: CD56dim CD16− (1·5 ± 1·1%) and CD56+ CD16− (2·1 ± 3·7%) (Fig. 2e). Given the fact that NK cells exert their function through direct cytotoxicity and by producing inflammatory and regulatory cytokines,39 we investigated whether CD8α− NK cells could become activated and produce cytokines upon stimulation with the known NK cell activating cytokines,
IL-2, IL-15 and IL-12. After 24 hr of incubation with IL-15, we detected an up-regulation of the early activation antigen CD69 on the surface of CD8α− and CD8α+ NK cells (P < 0·01, Fig. 3a). As for cytokine production potential, CD8α+ NK cells were capable of producing IFN-γ and TNF-α in response to 24 hr stimulation Apoptosis inhibitor with IL-15, whereas CD8α− NK cells showed an upward trend for TNF-α production, but did not produce IFN-γ (Fig. 3b,c). Of note, neither CD8α− nor CD8α+ NK cells significantly up-regulated CD69, IFN-γ or TNF-α in response to IL-12 (data not shown). Recently, a revised phenotypic analysis of chimpanzee
CD8α− NK cells showed that approximately 80% of CD8α− CD16+ cells are myeloid dendritic cells (mDCs) that express CD11c and HLA-DR on their surface. This suggests that in chimpanzees, CD8α− NK cells represent only approximately 20% of the cells present in the CD8α− CD16+ fraction.40 Based on this recent report, we re-evaluated our population of macaque CD8α− NK cells for expression of CD11c and HLA-DR. As shown in Fig. S1 (see Supplementary material) we found that, similarly to what was observed in chimpanzees, only approximately 35% (37·1 ± 10·7) of the cells within the CD8α− gate were negative for CD11c and HLA-DR expression and therefore could Alectinib purchase be considered true CD8α− NK cells. These CD8α− NK cells still showed four clear subpopulations based on their CD56 and CD16 expression patterns (see Supplementary material, Fig. S1c), but with slightly different proportions compared with those described in Fig. 2(d). Contaminating mDCs represented approximately 60% (61·7 ± 10·9%) of cells in the CD8α– CD16+ population, and were mostly CD56dim CD16+ and double-negative cells (see Supplementary material, Fig. S1d). These findings are in agreement with the small proportion of macaque CD8α− NK cells that expressed cytotoxic markers (Fig. 2b,c) and became activated in response to IL-2 and IL-15 stimulation (Fig. 3a).