CD4+ Natural Killer T Cells Potently Augment Aortic Root Atherosclerosis by Perforin- and Granzyme B-Dependent Cytotoxicity

Yi Li, Kelly To, Peter Kanellakis, Hamid Hosseini, Virginie Deswaerte, Peter Tipping, Mark J Smyth, Ban-Hock Toh, Alexander Bobik, Tin Kyaw

Rationale: CD4(+) Natural Killer T (NKT) cells augment atherosclerosis in ApoE(-/-) mice but their mechanisms of action are unknown. Objective: We investigated the roles of bystander T, B and NK cells, NKT cell derived IFN-γ, 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 ApoE(-/-)Rag2(-/-) 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 and NK cell-deficient ApoE(-/-)Rag2(-/-)γC(-/-) 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 IFN-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 ApoE(-/-)Jα18(-/-) mice. CD4(+) NKT cells deficient in IL-4, IFN-γ or IL-21 augmented atherosclerosis in ApoE(-/-)Jα18(-/-) 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 and MCP-1were 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 post-apoptotic necrosis and inflammation.