CD28 and atherosclerosis: To ascertain whether TERT-deficient Treg cells remain protective against atherosclerosis in vivo, we adoptively transferred a mixture of CD28−/− splenocytes, which lack the potential to differentiate into Treg cells, together with either WT or Tert−/− Tregs into Rag2−/−ApoE−/− mice, which lack mature lymphocytes.