Quantitative and Qualitative Differences in Proatherogenic NKT Cells in Apolipoprotein E–Deficient Mice

Background—Atherosclerosis is a disease marked by lipid accumulation and inflammation. Recently, atherosclerosis has gained recognition as an autoimmune-type syndrome characterized by increased activation of the innate and acquired immune systems. Natural killer T (NKT) cells have characteristics of both conventional T cells and NK cells and recognize glycolipid antigens presented in association with CD1d molecules on antigen-presenting cells. The capacity of NKT cells to respond to lipid antigens and modulate innate and acquired immunity suggests that they may play a role in atherogenesis. Methods and Results—We examined the role of NKT cells in atherogenesis and how the atherosclerotic environment affects the NKT cell population itself. The data show that CD1d-deficiency in male apolipoprotein E–deficient (apoE0) mice results in reduction in atherosclerosis, and treatment of apoE0 mice with α-galactosylceramide, a potent and specific NKT cell activator, results in a 2-fold increase in atherosclerosis. Interestingly, we demonstrate that α-galactosylceramide–induced interferon-γ responses and numbers of NKT cells in apoE0 mice show age-dependent qualitative and quantitative differences as compared with age-matched wild-type mice. Conclusions—Collectively, these findings reveal that hyperlipidemia and atherosclerosis have significant effects on NKT cell responses and that these cells are proatherogenic.