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Large-scale multi-ethnic cohorts offer unprecedented opportunities to elucidate the genetic factors influencing complex traits related to health and disease among minority populations. At the same time, the genetic diversity in these cohorts presents new challenges for analysis and interpretation. We consider the utility of race and/or ethnicity categories in genome-wide association studies (GWASs) of multi-ethnic cohorts. We demonstrate that race/ethnicity information enhances the ability to understand population-specific genetic architecture. To address the practical issue that self-identified racial/ethnic information may be incomplete, we propose a machine learning algorithm that produces a surrogate variable, termed HARE. We use height as a model trait to demonstrate the utility of HARE and ethnicity-specific GWASs.

Moderate alcohol consumption has been associated with a lower risk of coronary artery disease (CAD) in the general population but has not been well studied in US veterans. We obtained self-reported alcohol consumption from Million Veteran Program participants. Using electronic health records, CAD events were defined as 1 inpatient or 2 outpatient diagnosis codes for CAD, or 1 code for a coronary procedure. We excluded participants with prevalent CAD (n = 69,995) or incomplete alcohol information (n = 8,449). We used a Cox proportional hazards model to estimate hazard ratios and 95% confidence intervals for CAD, adjusting for age, gender, body mass index, race, smoking, education, and exercise. Among 156,728 participants, the mean age was 65.3 years (standard deviation = 12.1) and 91% were men. There were 6,153 CAD events during a mean follow-up of 2.9 years. Adjusted hazard ratios (95% confidence intervals) for CAD were 1.00 (reference), 1.02 (0.92 to 1.13), 0.83 (0.74 to 0.93), 0.77 (0.67 to 0.87), 0.71 (0.62 to 0.81), 0.62 (0.51 to 0.76), 0.58 (0.46 to 0.74), and 0.95 (0.85 to 1.06) for categories of never drinker; former drinker; current drinkers of ≤0.5 drink/day, >0.5 to 1 drink/day, >1 to 2 drinks/day, >2 to 3 drinks/day, and >3 to 4 drinks/day; and heavy drinkers (>4 drinks/day) or alcohol use disorder, respectively. For a fixed amount of ethanol, intake at ≥3 days/week was associated with lower CAD risk compared with ≤1 day/week. Beverage preference (beer, wine, or liquor) did not influence the alcohol-CAD relation. Our data show a lower risk of CAD with light-to-moderate alcohol consumption among US veterans, and drinking frequency may provide a further reduction in risk.

Much evidence indicates that atherosclerotic lesions are largely of an inflammatory nature. Activated macrophages and macrophage-derived foam cells laden with cholesterol esters are a major constituent of these lesions and can influence lesion formation via several potential mechanisms. One such mechanism is Fcgamma receptor activation and/or Fcgamma receptor-mediated clearance of immune complexes containing cholesterol, such as lipoprotein immune complexes. That this mechanism contributes to lesion formation would be further supported if Fcgamma receptor expression in arterial lesions were demonstrated. We therefore used monoclonal antibodies and immunocytochemical methods to analyze frozen sections of human arterial lesions for expression of each of the three primary classes of mononuclear phagocyte Fcgamma receptors. Approximately 800 sections of aorta, carotid, and coronary arteries obtained from five elderly donors were analyzed. The presence of macrophages was determined by assaying reactivity of a monoclonal antibody specific to CD163, which is expressed only on cells of the human mononuclear phagocyte lineage. Results indicate that highly cellular preatheromatous lesions contained numerous macrophages in the zone of proliferation that expressed each class of Fcgamma receptor (FcgammaRIA, FcgammaRIIA, and FcgammaRIIIA). Fcgamma receptor-positive cells were also present in medial and adventitial areas. Fcgamma receptor staining was both punctate and diffuse, the latter suggesting that soluble receptors were present in the extracellular matrix. These data further support that Fcgamma receptor-mediated clearance of immune complexes can occur in arterial lesions during atherogenesis. Expression of both the high affinity (FcgammaRIA) and lower affinity (FcgammaRIIA/FcgammaRIIIA) receptors indicates that mono- and multivalent IgG-containing immune complexes could engage Fcgamma receptors and influence lesion formation through several different inflammatory mechanisms triggered by receptor activation.

Recent recognition that an autoimmune myocarditis may precede, and result in, dilated cardiomyopathy has focused attention on immune mechanisms of myocardial injury. In this paper, we describe a model of chronic autoimmune myocarditis in the Lewis rat. The production of myocarditis has been previously described by this group and in brief is accomplished by a single tail vein infusion of activated T cells specific for a 17-amino acid peptide from rat cardiac myosin. In this report, animals were followed for approximately 6 months post-T-cell infusion. Hearts from animals which received cardiac myosin specific T cells all showed extensive fibrosis associated with ongoing inflammation. Apoptosis, identified by TdT-mediated dUTP nick end labelling (TUNEL), was identified as a mode of myocyte death in hearts with acute and chronic myocarditis but not in age- and sex-matched controls. Immunohistochemistry was used to characterize the immune infiltrate and adhesion molecules in hearts with chronic myocarditis and these findings were compared to hearts with acute myocarditis. We propose that this rat model of chronic myocarditis mimics human disease, since inflammation results in ventricular dilatation and myocyte hypertrophy reminiscent of dilated cardiomyopathy. This model offers potential for further investigation of immune, functional and possible therapeutic aspects of autoimmune related cardiomyopathies.

In the rat, autoimmune myocarditis can be produced by the infusion of activated myosin peptide specific, CD4 + , class II restricted, effector T cells. Whether antigen presenting cells (APCs), which interact with these effector T cells in the heart, are a fixed population of cells (resident dendritic, macrophage, or endothelial cells), or a dynamic bone marrow derived population has not yet been demonstrated in vivo . To study this question, bone marrow chimeras were generated using inbred Brown Norway (BN) rats, which are resistant to autoimmune myocarditis, and transplanting them after lethal irradiation with (Lewis×BN) F1 bone marrow. BN rats differ at both MHC loci from the susceptible inbred Lewis rats. Two months after bone marrow transplantation, chimeric animals received Lewis T cells specific for a myocarditogenic peptide antigen. To characterize the cardiac APCs, immunohistochemistry using a battery of antibodies including Lewis-specific and broadly reactive antibodies for both MHC class I and class II, was performed on chimeric hearts, with and without infused Lewis T cells, and non-transplanted BN control hearts. All chimeric rats infused with allogeneic (Lewis), anti-cardiac myosin peptide effector T cells displayed the lesions of myocarditis. Myocarditis was not present in non-transplanted BN controls given either Lewis or F1 derived myocarditogenic T cells, nor in chimeric animals which did not receive myocarditogenic T cells, thus excluding graft vs host disease as the explanation for the inflammation in chimeric hearts with myocarditis. Marrow derived cells expressing both Lewis class I and class II MHC molecules were demonstrated on perivascular cells in the myocardium of all chimeric animals, and on infiltrating cells in chimeric animals with myocarditis. Cells expressing Lewis-specific MHC antigens were not detected in the non-transplanted BN controls. Furthermore, immunohistochemistry using broadly reactive antibodies demonstrated MHC class II on perivascular cells with a dendritic morphology in all hearts but not on endothelial cells or cardiac myocytes. These results support the hypothesis that in vivo , cardiac APCs which result in MHC class II restricted, T cell induced myocarditis are a dynamic bone marrow derived population and not a fixed population. In order to address the potential requirement of MHC class I for the initiation of autoimmune myocarditis, myocarditogenic T cells derived from either Lewis or DA(RP) rats were infused into a member of the other strain. These strains share common MHC class II genes but differ at the MHC class I loci. Myocarditis identical to that produced in the syngeneic animal was successfully transferred by the MHC class I mismatched T cells, but only after the recipient animal's native immune system was mildly suppressed. These results further support the primary role for professional antigen presentation via MHC class II restriction to the effector T cells at the initiation of autoimmune myocarditis in the heart. Together, these experiments confirm that activated effector T cells, in order to produce myocarditis, require MHC class II compatible APCs in the heart, that these APCs are bone marrow derived, and will endogenously take up and present local antigens in the target organ after bone marrow reconstitution.