Opsonization of bacteria promotes Th17 responses. (A) Bacteria were coated on a 96-well plate, which were blocked and incubated with a control Ab, human serum, or purified IgG, followed by incubation with anti–human IgG-HRP and were subsequently developed. Data shown are mean ± SEM of triplicate measurement from 1 representative experiment of 3. (B) DCs and CD4⁺ T cells were incubated with bacteria that were preincubated or not in human serum. Intracellular levels of IFNγ and IL-17 were measured at day 12, after 5 hours of restimulation with PMA, ionomycin, and BFA. FACS plots shown are from 1 representative of 3 different donors.