Cytokine secretion during basal conditions. Primary human monocytes differentiated for four days were pre-incubated for 16 h serum-free media in presence or absence of LDL, AgLDL or VLDL (50 μg/ml). After pre-incubation, fresh media without lipoproteins, serum or growth factors was conditioned for 4 h and analyzed for cytokine protein content by ELISA. (A) Secreted IL-1β normalized to cell protein, (B) secreted TNF-α normalized to cell protein, (C) secreted IL-6 normalized to cell protein, (D) secreted IL-8 normalized to cell protein. Data represent mean ± SEM of cells from six different blood donors. * = P < 0.05, ** = P < 0.01 for respective lipoprotein treatment compared to control.