Cytokine secretion during stimulated conditions. Cell were pre-treated for 16 h with or without lipoproteins (50 μg/ml), then activated by incubation with exogenous TNF-α (1 ng/ml) for 4 h. For each lipoprotein pre-treatment, significances indicate comparisons between cells incubated in absence or presence of TNF-α. (A) Secreted IL-1β normalized to cell protein, (B) secreted IL-8 normalized to cell protein, (C) secreted IL-6 normalized to cell protein. Data represent mean ± SEM of cells from six different blood donors. * = P < 0.05, ** = P < 0.01 and *** = P < 0.001.