To further determine IL-22 production by naive and memory CD8+ T cells, we purified subsets of naive (CD45RA+) and memory (CD45RO+) CD8+ T cells from PBMCs and stimulated the two populations with anti-CD3 plus anti-CD28 in the presence or absence of IL-21 or IL-15. Interleukin-21 induced a large amount of IL-22 production by activated naive CD8+ T cells (Fig. 3d left graph). Anti-CD3 plus anti-CD28 induced a low level

of IL-22 and addition of IL-21 slightly increased IL-22 production by memory CD8+ T cells (Fig. 3d right graph). Naive CD8+ T cells produced Tamoxifen order IL-22 in greater amounts than memory CD8+ T cells with IL-21 stimulation. In addition, IL-15 had no effect on IL-22 production in naive CD8+ T cells but could induce IL-22 production by memory CD8+ T cells. Purified naive CD8+ T cells were labelled with CFSE and stimulated with anti-CD3 and anti-CD28 in the presence or absence of IL-21 for the indicated times. Cells were then collected for flow cytometric analysis for cell division. On day 3, both CD8+ T cells from CBMCs and CD8+ CD45RA+ T cells from PBMCs treated with IL-21 had more divisions than those cells without IL-21 treatment. On day 6, the proliferation of IL-21-treated CD8+ T cells was markedly higher than non-stimulated and anti-CD3 plus anti-CD28-stimulated selleck chemicals cells (Fig. 4a). In addition, on day 3, the cell number of CD8+ T cells from CBMCs was threefold to fourfold higher in culture with IL-21 than

in culture with anti-CD3 and anti-CD28 alone (Fig. 4b). Purified CD8+ T cells from CBMCs were cultured with anti-CD3 and anti-CD28 in the presence or absence of IL-21, and the expression of IL-21R was assessed by flow cytometry. The results showed that IL-21R was expressed at a low level on resting naive CD8+ T cells. Interleukin-21 up-regulated the expression of ADP ribosylation factor IL-21R following stimulation with anti-CD3 plus anti-CD28 (Fig. 5a). Moreover, stimulation of CD8+ T cells with anti-CD3 plus anti-CD28 resulted in higher levels of mean

fluorescence intensity (MFI) of IL-21R expression than untreated cells (P < 0·05). Addition of IL-21 further increased the MFI of IL-21R (Fig. 5a). We further examine the expression of granzyme B in IL-21-treated naive CD8+ T cells. The results showed that a low frequency of CD8+ T cells expressed granzyme B following anti-CD3 and anti-CD28 stimulation. Addition of IL-21 markedly enhanced granzyme B expression and IL-22+ CD8+ T cells produced granzyme B simultaneously (Fig. 5b). These findings indicate that both IL-22+ CD8+ and IL-22− CD8+ T cells contribute to the cytolytic function. Signalling through the IL-21R/γc may involve different JAK/STAT molecules in different responding cells. We therefore examined the phosphorylation of STATs in human naive CD8+ T cells following IL-21 stimulation. Stimulation of CD8+ T cells with IL-21 resulted in phosphorylation of STAT1 in more than 60% of cells and more than 30% of CD8+ T cells expressed phosphor-STAT3 and phosphor-STAT5.