Levels of circulating cytokines in patients with H7N9 avian influenza. Serum samples were prepared from 10 patients and 10 healthy controls. We carried out cytometric bead arrays to measure the concentrations of serum interleukin 1β (IL-1β), IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p70, tumor necrosis factor α (TNF-α), TNF-β and interferon γ (IFN-γ) in individual samples. Data shown are the mean values of individual cytokines in each participant from two separate experiments, which we analyzed by Mann–Whitney U test. Under our experimental conditions, we found no detectable levels of serum IL-1β, IL-4, IL-5, IL-12p70, TNF-α, TNF-β or IFN-γ in these participants (data not shown). Error bars were shown in each column.