Lipoproteins act as vehicles for lipid antigen delivery and activation of invariant natural killer T cells.

Invariant natural killer T (iNKT) cells act at the interface between lipid metabolism and immunity because of their restriction to lipid antigens presented on CD1d by antigen-presenting cells (APCs). How foreign lipid antigens are delivered to APCs remains elusive. Since lipoproteins routinely bind glycosylceramides structurally similar to lipid antigens, we hypothesized that circulating lipoproteins form complexes with foreign lipid antigens. In this study, we used 2-color fluorescence correlation spectroscopy to show, for the first time to our knowledge, stable complex formation of lipid antigens α-galactosylceramide (αGalCer), isoglobotrihexosylceramide, and OCH, a sphingosine-truncated analog of αGalCer, with VLDL and/or LDL in vitro and in vivo. We demonstrate LDL receptor-mediated (LDLR-mediated) uptake of lipoprotein-αGalCer complexes by APCs, leading to potent complex-mediated activation of iNKT cells in vitro and in vivo. Finally, LDLR-mutant PBMCs of patients with familial hypercholesterolemia showed impaired activation and proliferation of iNKT cells upon stimulation, underscoring the relevance of lipoproteins as a lipid antigen delivery system in humans. Taken together, circulating lipoproteins form complexes with lipid antigens to facilitate their transport and uptake by APCs, leading to enhanced iNKT cell activation. This study thereby reveals a potentially novel mechanism of lipid antigen delivery to APCs and provides further insight into the immunological capacities of circulating lipoproteins.

Therapeutic strategies targeting inflammation and immunity in atherosclerosis: how to proceed?

Atherosclerosis is a chronic inflammatory disease of the arterial wall, characterized by the formation of plaques containing lipid, connective tissue and immune cells in the intima of large and medium-sized arteries. Over the past three decades, a substantial reduction in cardiovascular mortality has been achieved largely through LDL-cholesterol-lowering regimes and therapies targeting other traditional risk factors for cardiovascular disease, such as hypertension, smoking, diabetes mellitus and obesity. However, the overall benefits of targeting these risk factors have stagnated, and a huge global burden of cardiovascular disease remains. The indispensable role of immunological components in the establishment and chronicity of atherosclerosis has come to the forefront as a clinical target, with proof-of-principle studies demonstrating the benefit and challenges of targeting inflammation and the immune system in cardiovascular disease. In this Review, we provide an overview of the role of the immune system in atherosclerosis by discussing findings from preclinical research and clinical trials. We also identify important challenges that need to be addressed to advance the field and for successful clinical translation, including patient selection, identification of responders and non-responders to immunotherapies, implementation of patient immunophenotyping and potential surrogate end points for vascular inflammation. Finally, we provide strategic guidance for the translation of novel targets of immunotherapy into improvements in patient outcomes.

Immunometabolic factors in adolescent chronic disease are associated with Th1 skewing of invariant Natural Killer T cells.

Invariant Natural Killer T (iNKT) cells respond to the ligation of lipid antigen-CD1d complexes via their T-cell receptor and are implicated in various immunometabolic diseases. We considered that immunometabolic factors might affect iNKT cell function. To this end, we investigated iNKT cell phenotype and function in a cohort of adolescents with chronic disease and immunometabolic abnormalities. We analyzed peripheral blood iNKT cells of adolescents with cystic fibrosis (CF, n = 24), corrected coarctation of the aorta (CoA, n = 25), juvenile idiopathic arthritis (JIA, n = 20), obesity (OB, n = 20), and corrected atrial septal defect (ASD, n = 25) as controls. To study transcriptional differences, we performed RNA sequencing on a subset of obese patients and controls. Finally, we performed standardized co-culture experiments using patient plasma, to investigate the effect of plasma factors on iNKT cell function. We found comparable iNKT cell numbers across patient groups, except for reduced iNKT cell numbers in JIA patients. Upon ex-vivo activation, we observed enhanced IFN-γ/IL-4 cytokine ratios in iNKT cells of obese adolescents versus controls. The Th1-skewed iNKT cell cytokine profile of obese adolescents was not explained by a distinct transcriptional profile of the iNKT cells. Co-culture experiments with patient plasma revealed that across all patient groups, obesity-associated plasma factors including LDL-cholesterol, leptin, and fatty-acid binding protein 4 (FABP4) coincided with higher IFN-γ production, whereas high HDL-cholesterol and insulin sensitivity (QUICKI) coincided with higher IL-4 production. LDL and HDL supplementation in co-culture studies confirmed the effects of lipoproteins on iNKT cell cytokine production. These results suggest that circulating immunometabolic factors such as lipoproteins may be involved in Th1 skewing of the iNKT cell cytokine response in immunometabolic disease.

Incidence of cardiovascular events and vascular interventions in patients with type 2 diabetes.

OBJECTIVE: Diabetes mellitus is associated with an increased risk for cardiovascular morbidity and mortality. The vascular burden in terms of incidence of cardiovascular events (CVE) and vascular interventions is however poorly quantified. In this study we evaluated the incidence rates of CVE and vascular interventions in patients with type 2 diabetes (T2DM) with and without cardiovascular disease (CVD) in comparison to patients without type 2 diabetes. RESEARCH DESIGN AND METHODS: In a cohort of 9.808 high-risk patients with and without cardiovascular disease and type 2 diabetes originated from the ongoing, single-center prospective SMART (Second Manifestations of ARTerial disease) cohort, the number and incidence rates of CVE and interventions were calculated. The incidence rates were adjusted for confounders using Poisson regression models. CVE were defined as vascular death, stroke and myocardial infarction (MI). Interventions were defined as percutaneous coronary intervention, coronary artery bypass grafting, percutaneous transluminal angioplasty or stenting of the peripheral arteries and amputation. RESULTS: Patients with T2DM and CVD had a 4-fold higher incidence rate of CVE and a 8-fold higher incidence rate of vascular interventions compared to high-risk patients without T2DM and CVD after adjusting for confounders. The incidence rate for the composite of non-fatal MI, non-fatal stroke and vascular death was 5.8 per 1000person-years in patients without T2DM or CVD at baseline, 15.2 per 1000person-years in patients with T2DM but without CVD at baseline, 26.0 per 1000person-years in patients without T2DM but with CVD and 40.7 per 1000person-years in patients with both T2DM and CVD at baseline. A similar increasing incidence rate was seen for all vascular interventions from patients without T2DM or CVD to patients with both T2DM and CVD. CONCLUSIONS: Patients with type 2 diabetes or CVD are subject to an increased incidence of cardiovascular events and interventions compared to high-risk patients without type 2 diabetes or vascular disease. Patients with type 2 diabetes and CVD have the highest incidence of new cardiovascular diseases and vascular interventions when compared to patients without type 2 diabetes and CVD. These results underline the need for optimal risk factor treatment as well as the need for new prevention and treatment strategies in this very high risk population.