Effects of human protein S on intracellular cholesterol accumulation in THP-1 macrophages. THP-1 macrophages were treated with 20 μg/mL protein S and 50 μg/mL AcLDL for 24 hours. The cellular cholesterol content was measured using a Wako Chemicals cholesterol assay kit. Values are mean plus or minus SD of 3 experiments. *P < .05 versus untreated controls. (A) Cholesterol ester content. (B) Free cholesterol content.