CD28 and atherosclerosis: Conversely, reconstitution with CD80−/−/CD86−/− or CD28−/− bone marrow in LDLR−/− mice inhibited Treg development and exacerbated atherosclerosis, indicating that the CD80/CD86-CTLA4 axis in bone marrow-derived cell types is crucial for Treg development and Treg suppression of atherosclerosis.