ApoE facilitates the activation of CD1-restricted natural killer T (NKT) cells. Inactivated NKT cells express surface marker of NK1.1 and a semiinvariant T cell receptor (TCR). ApoE facilitates lipid antigen-presentation by CD1 positive antigen presenting cells (APCs) mainly through binding to low-density lipoprotein receptor (LDLR). CD1 molecules present lipid antigens to NKT cells. Upon ligation to CD1 via TCR, naive NKT cells are activated, and respond rapidly to secrete high levels of IFN- and IL-4, which play a critical role in the modulation of immune and inflammatory responses.