Human peripheral blood was obtained from healthy volunteers with approval from the institutional review board as described previously.27 (link) Peripheral blood mononucleated cells were isolated from human peripheral blood using Histopaque (Sigma, Germany) following negative isolation with magnetic beads (Stem Cell, Canada), yielding >95% CD14+ monocytes. Cells were cultured in macrophage serum-free medium (Life Technologies, USA) supplemented with Nutridoma SP (Roche, Germany) and penicillin/streptomycin (Sigma, Germany) for 6 days in the presence of 100 ng/mL recombinant human macrophage colony-stimulating factor (Peprotech, USA). Macrophages were exposed to 15 μg/mL oxidized LDL (oxLDL) (Hycultec, Germany) in addition to 100 ng/mL CCL19 or 100 ng/mL CCL21 for 24 hours. The experiment was repeated five times. After washing the cells, we performed Oil Red O staining. For Oil Red O-staining analysis, we used the program ImageJ and the plugin colored convolution for ImageJ (National Institutes of Health). We measured the positively stained area in relation to the total area of the cells for each group. Untreated macrophages served as negative controls.