CD1d-dependent Activation of NKT Cells Aggravates Atherosclerosis

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Abstract
Adaptive and innate immunity have been implicated in the pathogenesis of atherosclerosis. Given their abundance in the lesion, lipids might be targets of the atherosclerosis-associated immune response. Natural killer T (NKT) cells can recognize lipid antigens presented by CD1 molecules. We have explored the role of CD1d-restricted NKT cells in atherosclerosis by using apolipoprotein E-deficient (apoE-/-) mice, a hypercholesterolemic mouse model that develops atherosclerosis. ApoE-/- mice crossed with CD1d-/- (CD1d-/-apoE-/-) mice exhibited a 25% decrease in lesion size compared with apoE-/- mice. Administration of alpha-galactosylceramide, a synthetic glycolipid that activates NKT cells via CD1d, induced a 50% increase in lesion size in apoE-/- mice, whereas it did not affect lesion size in apoE-/-CD1d-/- mice. Treatment was accompanied by an early burst of cytokines (IFNgamma, MCP-1, TNFalpha, IL-2, IL-4, IL-5, and IL-6) followed by sustained increases in IFNgamma and IL-4 transcripts in the spleen and aorta. Early activation of both T and B cells was followed by recruitment of T and NKT cells to the aorta and activation of inflammatory genes. These results show that activation of CD1d-restricted NKT cells exacerbates atherosclerosis.