Abstract 117: CCR7-deficiency Prevents Dendritic Cell-dependent T-cell Priming, And Thereby Reduces Atherosclerotic Plaque Development
Background: The chemokine receptor CCR7 is required for the migration of dendritic cells (DC) into lymph nodes, thereby mediating T-cell priming and the induction of immune responses. Oxidatively modified low density lipoprotein (oxLDL) is considered as a pivotal contributor to atherogenesis. In fact, oxLDL has been suggested to act as an antigen which promotes Th1-cell priming characterized by a specific pro-inflammatory cytokine response. It was previously demonstrated that Th1 cytokine levels are enhanced in atherosclerosis: Moreover, a specific set of T-cell receptors has recently been identified in atherosclerotic lesions. We here investigated whether CCR7-deficiency influences oxLDL induced DC-dependent T-cell priming, thereby reducing atherosclerotic plaque development
Methods: Male CCR7 −/− mice were crossed with LDLR−/− mice. 10-week-old mice were fed with a high-cholesterol diet for 12 weeks. Aortic plaque area was determined en face by Oil Red O staining. Immune cells within the mesenteric lymph nodes (MLN) were analyzed by FACS Plasma lipids and INFγ-levels were analysed by ELISA. DC were differentiated from bone marrow cells by stimulation with GM-CSF. Following stimulation of DC with native and oxLDL we analyzed CCR7 mRNA expression by real time PCR, CCR7 protein expression by immunocytochemistry and DC migration towards CCL19 by a transwell assay. OxLDL-dependent T cell priming was analyzed in a mixed lymphocyte reaction and monitored by a proliferation assay and by FACS-analysis.
Results: After feeding, plasma cholesterol fractions did not differ between the groups, whereas atherosclerotic plaque formation was significantly reduced in CCR7−/−/LDL−/− mice. CCR7-deficiency reduces total numbers of T- cells and DC in mesenteric lymph nodes (MLN). The Th1-cytokine response as determined by INFγ-levels was significantly reduced in CCR7−/−/ LDLR−/− mice. OxLDL but not native LDL promoted DC maturation, CCR7 expression and DC migration. Furthermore, stimulation of DC with oxLDL induced T-cell proliferation and expression of the oxLDL specific T-cell receptor Vβ6.
Conclusion: CCR7 critically influences atherosclerotic plaque development by enabling oxLDL dependent T-cell priming by DC in secondary lympoid organs.