Differential effects of a saturated and a monounsaturated fatty acid on MHC class I antigen presentation.
Lipid overload, associated with metabolic disorders, occurs when fatty acids accumulate in non-adipose tissues. Cells of these tissues use major histocompatibility complex (MHC) class I molecules to present antigen to T cells in order to eliminate pathogens. As obesity is associated with impaired immune responses, we tested the hypothesis that the early stages of lipid overload with saturated fatty acids (SFA) alters MHC class I antigen presentation. Antigen presenting cells (APC) were treated with either the saturated palmitic acid (PA), abundant in the high fat Western diet, or the monounsaturated oleic acid (OA), a component of the Mediterranean diet. PA-treatment lowered APC lysis by activated cytotoxic T lymphocytes and inhibited APC ability to stimulate naïve T cells. Inhibition of immune responses with PA was due to a significant reduction in MHC class I surface expression, inhibition in the rate of APC-T-cell conjugation, and lowering of plasma membrane F-actin levels. OA-treatment had no effect on antigen presentation and upon exposure with PA, prevented the phenotypic effects of PA. OA-treatment conferred protection against changes in antigen presentation by accumulating fatty acids into triglyceride-rich lipid droplets of APC. Our findings establish for the first time a link between the early stages of lipid overload and antigen presentation and suggest that dietary SFA could impair immunity by affecting MHC I-mediated antigen presentation; this could be prevented, paradoxically, by accumulation of triglycerides rich in monounsaturated fatty acids.
Department of Biology, Johns Hopkins University, 3400 North Charles Street, Mudd Hall Room 45, Baltimore, MD 21218, USA. saameshaikh@gmail.com
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Shaikh
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Mitchell
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Carroll
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Li
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Schneck
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Edidin
D000818:Animals; D017951:Antigen Presentation / Q000187:drug effects* / Q000276:immunology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects; D003602:Cytotoxicity, Immunologic / Q000187:drug effects / Q000276:immunology; D005227:Fatty Acids / Q000494:pharmacology*; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology*; D005434:Flow Cytometry; D015395:Histocompatibility Antigens Class I; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology; D051379:Mice; D018613:Microscopy, Confocal; D019301:Oleic Acid / Q000494:pharmacology; D019308:Palmitic Acid / Q000494:pharmacology; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000276:immunology
D005227:Fatty Acids; D005229:Fatty Acids, Monounsaturated; D015395:Histocompatibility Antigens Class I; D019301:Oleic Acid; D019308:Palmitic Acid