Autologous platelets interfere with Gp96-induced DC maturation.

Human monocytes were cultured with granulocyte macrophage–colony-stimulating factor and IL-4 to obtain immature DCs. After 6 days, 4 × 10⁶ thrombin-activated platelets from the same donor were preincubated with 20 μg/mL Gp96 in a 96-well plate for 45 minutes, followed by the addition of 2 × 10⁵ immature DCs per well. (A) Cytokine concentrations of IL-12, TNF-α, and IL-10 in the cell culture supernatant were determined by enzyme-linked immunosorbent assay after 24 hours. (B) The maturation of DCs was measured by determining the number of CD83⁺ and CD86^high cells by flow cytometry. Values for DCs without platelets are shown as filled bars; DC-platelet cocultures are shown as open bars. Data shown are representative for 3 independent experiments with cells from different donors.