CD4 and atherosclerosis: Interestingly, under AL feeding, CD resulted in a relative increase of CD4+ T central memory (Tcm) cells (CD44+ CD62L+) (i.e., cells without effector function that were formed upon activation of naive cells for augmented immune response upon reactivation) at ZT6 and ZT18 (Fig. 4g), which may indicate that T cells have been activated earlier in the process of atherosclerosis development.