One-week-old human M-CSF differentiated monocyte-derived macrophage cultures were incubated 1 day with 50 μg/ml AcLDL to induce macrophage deposition of extracellular cholesterol microdomains. Following rinsing, macrophage cultures were incubated 1 day with the indicated additions (20 μg ApoA-I, 100 μg/ml peptide, and 125 μg/ml sphingomyelin complexed with 100 μg/ml peptide 5A) without AcLDL. In the left column, cholesterol microdomains were visualized by fluorescence microscopy using anti-cholesterol microdomain Mab 58B1 (green), and nuclei were imaged with DAPI fluorescence staining (blue). In the right column, macrophages were visualized using phase-contrast microscopy. Left and right columns show corresponding microscopic fields. AcLDL, acetylated low-density lipoprotein; f/b, followed by; 5A-SPH, 5A-sphingomyelin complex. Bar = 50 μm and applies to all.