IL-21 and IL-23 contribute to the induction of Tc17 cells by Th17. Purified dendritic cells, CD8+ T cells and CD4+ T cells were cocultured using a combination of cytokines and blocking antibodies. For Th1, recombinant mouse IL-12 was used and for Th17, recombinant mouse IL-6, IL-23 and TGF-β and a blocking antibody to IFN-γ were used. The polarized cells were washed but not rested before being cocultured. Purified CD8+ T cells from OT-1 mice were cultured in vitro with SIINFEKL peptide and IL-17A, IL-21 and IL-23 (A). To block, IL-17A, IL-21 and IL-23, antibodies against these cytokines were used (B). Cells were gated on CD3+CD8+ T cells. In (C), Upper panel shows effect of IL-21 and /or Il-23 on IL-17 producing CD8+ T cells and lower panel shows similar comparison for IFN-γ production. Each experiment was performed three times. Mann Whitney test was used to determine significance. * P<0.05, and ****P<0.0001.