A) Monocyte-derived macrophages from normal human donors were cultured in medium alone for 12 h and then incubated with antibodies specific for cell surface markers HLA-DR, CD11b and CD206 (solid line), or with isotype control antibodies (dotted line). B) Macrophages from the same human donors were stimulated for 36 h with LPS (50ng/ml; dotted line), or left untreated (solid line) before incubation with antibodies specific for HLA-DR, CD11b and CD206. Approximately 95% of monocyte-derived macrophages from normal human donors expressed high levels of HLA-DR, CD11b and CD206, which is indicative of their macrophage lineage. The data shown are representative of 2 independent experiments.