FcγRIIa ligation up-regulates Th17-promoting cytokines via synergy with TLR stimulation. (A-B) DCs were stimulated with plate-bound IgG, (A) LPS, (B) PGN, or a combination. After 24 hours, cytokine levels in the supernatant were determined by ELISA. Data shown are from 1 representative experiment of at least 5 experiments with different donors. (C) Fold-increase in cytokine production on LPS or PGN stimulation combined with plate-bound IgG stimulation compared with LPS or PGN stimulation without plate-bound IgG. For every cytokine, every dot represents a different donor tested in an individual experiment. (D) DCs were preincubated for 30 minutes with or without a blocking Ab against FcγRIIa, after which cells were stimulated with LPS or PGN in combination with plate-bound IgG. Data shown are from 1 representative experiment of 3 independent experiments with different donors. (E) DCs were preincubated for 30 minutes with or without a blocking Ab against FcγRIIa. Subsequently, the cells were stimulated with LPS or PGN in combination with plate-bound IgG and cocultured with CD4⁺ T cells. IL-17 levels were measured by ELISA at day 12, after restimulation with a CD3-specific and a CD28-specific Ab. Data shown are from 1 representative of 3 different donors. Error bars indicate SEM; *P < .05, **P < .01; ns indicates not significant; paired t test.