Cytokine assays
The serum concentrations of the cytokines IL-2, IL-4, IL-6, IL-10, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α, were measured using the Cytometric Bead Array Kit (BD Biosciences, San Diego, CA, USA). The serum concentration of IL-8 was measured using Human CXCL8/IL-8 Quantikine enzyme-linked immunosorbent assay (ELISA) kit (R&D Systems, Minneapolis, MN, USA). The lower detection limits for IL-2, IL-4, IL-6, IL-8, IL-10, IFN-γ, and TNF-α, were 2.6, 2.6, 3.0, 3.5, 2.8, 7.1, and 2.8 pg/mL, respectively.