Aim To investigate the effects of low density lipoprotein immune complexes (LDL-IC) on the accumulation of cholesteryl ester (CE) in mouse peritoneal macrophages and on the secretion of nitric oxide (NO) from the macrophages. Methods LDL was isolated from fresh human plasma by ultracentrifugation, and then LDL-IC was prepared by incubating LDL with IgG fraction of a sheep anti-LDL antiserum in vitro. After mouse peritoneal macrophages were incubated with LDL-IC, cellular cholesteryl ester mass was quantified by an enzymatic fluorometric methods and the morphological observation and histochemistry of macrophages were performed. In addition, nitric oxide secreted from macrophages to the medium was measured by nitric acid reductase method. Results The levels of cellular CE in macrophages were increased markedly with LDL-IC dose dependent manner, which was significantly higher than that induced by corresponding level of oxidized LDL(ox-LDL)(p<0.01). Whereas native LDL and apoB-IgG did not show any effect on the level of cellular CE. Morphologically, after exposure to LDL-IC, macrophages exhibited a phenotype typical of lipid-laden foam cell, becoming strongly stained with scarlet. In addition, the content of NO in the medium released from the macrophages were decreased and also showed a LDL-IC dose dependent manner. Conclusion LDL-IC participates in atherosclerotic formation not only by inducing the formation of foam cell, but also by damaging the function of NO of macrophages.