Adoptive transfer of MHCII−/− B cells into B cell–deficient Apoe–/– mice also led to decreased atherosclerosis and decreased IgG, but this time, IgM levels were reduced.33 Conversely, Williams et al,60 using Cd19Cre/+MHCIIfl/flLdlr−/− mice and MHCIIfl/flLdlr−/− littermates, did not find any effect in atherosclerosis development. This evidence concerns the gene APOE and atherosclerosis.