In the course of studies on the role of NKT cells on lipoprotein metabolism and atherosclerosis in Ldlr−/− mice, we have noted a selective and substantial increase in the plasma titer of E06 IgM in CD1d-deficient Ldlr−/− (Cd1d−/−Ldlr−/−) mice compared to Ldlr−/− and Jα18 deficient Ldlr−/− (Jα18−/−Ldlr−/−) mice. This evidence concerns the gene CD1D and atherosclerosis.