CD4+ natural killer T cells potently augment aortic root atherosclerosis by perforin-and granzyme b-dependent cytotoxicity

Abstract

RATIONALE:: CD4+ natural killer T (NKT) cells augment atherosclerosis in apolipoprotein E-deficient (ApoE) mice but their mechanisms of action are unknown. OBJECTIVES:: We investigated the roles of bystander T, B, and NK cells; NKT cell-derived interferon-γ, interleukin (IL)-4, and IL-21 cytokines; and NKT cell-derived perforin and granzyme B cytotoxins in promoting CD4+ NKT cell atherogenicity. METHODS AND RESULTS:: Transfer of CD4+ NKT cells into T-and B-cell-deficient ApoERag2 mice augmented aortic root atherosclerosis by ≈75% that was ≈30% of lesions in ApoE mice; macrophage accumulation similarly increased. Transferred NKT cells were identified in the liver and atherosclerotic lesions of recipient mice. Transfer of CD4+ NKT cells into T-, B-cell-deficient, and NK cell-deficient ApoERag2γC mice also augmented atherosclerosis. These data indicate that CD4+ NKT cells can exert proatherogenic effects independent of other lymphocytes. To investigate the role of NKT cell-derived interferon-γ, IL-4, and IL-21 cytokines and perforin and granzyme B cytotoxins, CD4+ NKT cells from mice deficient in these molecules were transferred into NKT cell-deficient ApoEJα18 mice. CD4+ NKT cells deficient in IL-4, interferon-γ, or IL-21 augmented atherosclerosis in ApoEJα18 mice by ≈95%, ≈80%, and ≈70%, respectively. Transfer of CD4+ NKT cells deficient in perforin or granzyme B failed to augment atherosclerosis. Apoptotic cells, necrotic cores, and proinflammatory VCAM-1 (vascular cell adhesion molecule) and MCP-1 (monocyte chemotactic protein) were reduced in mice receiving perforin-deficient NKT cells. CD4+ NKT cells are twice as potent as CD4+ T cells in promoting atherosclerosis. CONCLUSIONS:: CD4+ NKT cells potently promote atherosclerosis by perforin and granzyme B-dependent apoptosis that increases postapoptotic necrosis and inflammation.