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  • Title: Dyslipidemia inhibits Toll-like receptor-induced activation of CD8alpha-negative dendritic cells and protective Th1 type immunity.
    Author: Shamshiev AT, Ampenberger F, Ernst B, Rohrer L, Marsland BJ, Kopf M.
    Journal: J Exp Med; 2007 Feb 19; 204(2):441-52. PubMed ID: 17296788.
    Abstract:
    Environmental factors, including diet, play a central role in influencing the balance of normal immune homeostasis; however, many of the cellular mechanisms maintaining this balance remain to be elucidated. Using mouse models of genetic and high-fat/cholesterol diet-induced dyslipidemia, we examined the influence of dyslipidemia on T cell and dendritic cell (DC) responses in vivo and in vitro. We show that dyslipidemia inhibited Toll-like receptor (TLR)-induced production of proinflammatory cytokines, including interleukin (IL)-12, IL-6, and tumor necrosis factor-alpha, as well as up-regulation of costimulatory molecules by CD8alpha(-) DCs, but not by CD8alpha(+) DCs, in vivo. Decreased DC activation profoundly influenced T helper (Th) cell responses, leading to impaired Th1 and enhanced Th2 responses. As a consequence of this immune modulation, host resistance to Leishmania major was compromised. We found that oxidized low-density lipoprotein (oxLDL) was the key active component responsible for this effect, as it could directly uncouple TLR-mediated signaling on CD8alpha(-) myeloid DCs and inhibit NF-kappaB nuclear translocation. These results show that a dyslipidemic microenvironment can directly interfere with DC responses to pathogen-derived signals and skew the development of T cell-mediated immunity.
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