CD11c + Dendritic Cells Maintain Antigen Processing, Presentation Capabilities, and CD4 + T-Cell Priming Efficacy Under Hypercholesterolemic Conditions Associated With Atherosclerosis

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Abstract
Recent reports suggest dyslipidemia impairs dendritic cell (DC) function and adaptive immunity. This study aimed to characterize the effect of hypercholesterolemia on antigen-presenting cell function of DCs and DC-dependent CD4+ T-cell responses. DCs incubated in vitro with acetylated low-density lipoprotein cholesterol with or without an acyl-coenzyme A:cholesterol acyl-transferase inhibitor maintained their ability to prime CD4+ T cells. Analysis of T-cell proliferation and interferon-γ and tumor necrosis factor-α production after ex vivo coculture of naïve CD4+ T cells with splenic, inguinal, or iliac DCs from low-density lipoprotein receptor–deficient (LDLR−/−) or apolipoprotein E–deficient (ApoE−/−) mice fed an atherogenic diet highlighted DC efficacy in effector T-cell generation under hypercholesterolemic conditions. Adoptive transfer of carboxyfluorescein diacetate, succinimidyl ester (CFSE)-labeled naïve CD4+ T cells in LDLR−/− recipients and subsequent immunization demonstrated effective priming of naïve T cells in hypercholesterolemic mice. CFSE dilution analyses revealed that hypercholesterolemic DCs were equipotent in naïve CD4+ T-cell priming efficacy with normocholesterolemic DCs. Quantitative real-time PCR and flow cytometric analyses demonstrated that DC expression of multiple molecules involved in antigen processing, presentation, and T-cell stimulation remained unaltered by dyslipidemia. Finally, endogenous antigen-primed CD4+ T cells responded equivalently to a secondary ex vivo antigenic challenge, regardless of whether they were primed in vivo under hypercholesterolemic or control conditions, demonstrating that all essential steps in CD4+ T-cell responses remain intact under atherogenic conditions. This study affirms that the adaptive immune response prevails under the hypercholesterolemic conditions present in atherosclerosis. In particular, DCs remain functional antigen-presenting cells and maintain their ability to prime CD4+ T cells even when cholesterol-loaded.