Down-regulation of protective T_H1 response by T_H17-related cytokines. (A) Healthy donor PBMCs were activated with T_H1 polarizing cytokines as described in “Intracellular IL-17–producing T_h17 cell analysis by flow cytometry” in presence or absence of IL-17 and IL-22 for 12 days. Cells were treated with PMA and ionomycin, stained for intracellular IFN-γ, and evaluated by flow cytometry. IFN-γ–producing cell number was evaluated in CD69+ cell population in CD4 gated cells. A representative dot plot analysis showing percentage of cells that are positive for intracellular IFN-γ within gated CD4 population. (B) Composite results of 9 experiments presented in a bar graph. Results are mean plus or minus SEM in healthy donors. (C) Healthy donor PBMCs were activated with TH1 polarizing cytokines in the presence or absence of IL-17 and IL-22 for 6 days, and supernatants were analyzed for IFN-γ by ELISA. *P < .05.