Atherosclerosis is a chronic disease that causes various cardiovascular complications.It has been realized that cellular and humoral immunity plays crucial roles in atherogenic lesion formation.In this study the effects of lipopolysaccharide (LPS) and interleukin-10 (IL-10) on the formation of foam cells during the early stages of atherosclerosis have been investigated.Macrophage was induced by phorbol myristate acetate (PMA) treatment on THP-1 cells.The cells were further stimulated by ox-LDL,ox-LDL plus LPS,ox-LDL plus IL-10 and LPS.By using an oil red O staining technique,the formation of foam cells was evaluated by lipid granules formation in the cells.The ratio of foam cell formation was increased from (9.77±1.70)% to (16.27±2.27)% after 24 h stimulation with ox-LDL,and the increase was observed with incubating time.The foam cells were significantly increased in the presence of LPS in a dose-dependent manner.The maximum increase of about 40% was observed.However,the significant elevation by LPS was abrogated when IL-10 was added.These results indicated that IL-10 can effectively prevent the formation of foam cells induced by ox-LDL with or without LPS.This study demonstrates that oxLDL can cause foam cell formation from macrophages in vitro.LPS can significantly accelerate this event.IL-10,an anti-inflammatory cytokine,can inhibit the effect of oxLDL and LPS.These results indicate that inflammatory effects in blood vessels can speed up foam cell formation.The inhibitive effect of IL-10 is an important factor for delaying atherosclerosis processes.