Low levels of IgM antibodies to phosphorylcholine predict cardiovascular disease in 60-year old men: Effects on uptake of oxidized LDL in macrophages as a potential mechanism Ulf de Faire a, b, * , Jun Su c , Xiang Hua c , Anna Frostegård c , Mats Halldin a , Mai-Lis Hellenius d , Max Wikstro ¨m b , Ingrid Dahlbom e , Hans Gro ¨ nlund f , Johan Frostegård c a Division of Cardiovascular Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden b Department of Cardiology, Karolinska University Hospital, Solna, Sweden c Department of Medicine, Karolinska University Hospital, Huddinge, Karolinska Institutet, Stockholm, Sweden d Department of Medicine, Karolinska University Hospital, Solna, Sweden e Department of Woman’s and Children’s Health, Uppsala University, Uppsala, Sweden f Department of Clinical Immunology, Karolinska University Hospital, Solna, Sweden article info Article history: Received 15 May 2009 Accepted 20 May 2009 Keywords: Atherosclerosis Innate immunity Natural antibodies Phosphorylcholine Cardiovascular disease abstract Objective: We here determine the role of IgM antibodies against phosphorylcholine (anti-PC) in prediction of cardiovascular disease (CVD) and on macrophage uptake of Oxidized LDL (OxLDL). Methods: From a screening of 4232 subjects, 60-year-old (2039 men and 2193 women), 211 incident cases of CVD (myocardial infarction, ischemic stroke, or hospitalized angina pectoris) and 633 age- and sex-matched controls were identified through a 5–7 year follow-up. Serum levels of IgM anti-PC was determined by ELISA. Anti-PC was extracted from pooled human IgM and the effect of anti-PC on the uptake of OxLDL was studied by FACScan. Results: Relative risks (RR) with 95% confidence intervals (CI) by quartiles of anti-PC levels with quartile 4 set as the reference value (RR ¼ 1.0) and adjusted for smoking, BMI, type II diabetes, hyper- cholesterolaemia, and high blood pressure yielded an excess risk for CVD only for those within the lowest quartile of anti-PC values with an RR of 1.37 (CI 0.87–2.16). However, for men stronger associations were noted with increasing multivariately adjusted RRs from quartile 4 to quartile 1. Subjects within quartile 1 (values below 29.7 U/ml) had a significantly increased RR of 1.96 (CI 1.09–3.55). Further adjustments for hsCRP gave essentially the same results. No excess risk was noted for women. Specific anti-PC could be extracted from IgM and these antibodies inhibited macrophage uptake of OxLDL. Conclusions: Low IgM anti-PC could be a novel risk marker for CVD among men. One possible mechanism could be inhibition of uptake of oxLDL in macrophages. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Atherosclerosis is the major underlying vascular cause of cardio- vascular disease (CVD) such as stroke, myocardial infarction (MI) and unstable angina occurring when atherosclerotic plaques rupture leading to ischemia, atherothrombosis and cell damage. Character- ization of subjects at risk have been mainly based upon traditional risk factors like age, male sex, smoking, hypertension, hyper- and dyslipidaemias, elevated apo B/apoA1 ratios, diabetes, and central obesity. However, other factors reflecting pro-inflammatory and immunogenic mechanisms now attract increasing attention, and atherosclerosis can be characterized as an inflammatory disease[1,2]. Oxidization of low density lipoprotein (LDL), a hallmark of the atherosclerotic process, facilitates the uptake of LDL in macro- phages, which is generally believed to be of importance in atherogenesis. Oxidized LDL (OxLDL) is also proinflammatory and immunogenic[3,4] containing other oxidized products including platelet activating factor (PAF)-like lipids, where phosphorylcho- line (PC) is a main epitope[5–7]. PC is essential for binding to the PAF-receptor and also other proinflammatory effects of OxLDL can be caused by PAF-like lipids[5–8]. Furthermore, PC is a component on some bacteria and apoptotic cells where it can be recognized by anti-PC antibodies[9]. * Corresponding author at: Division of Cardiovascular Epidemiology, IMM, Kar- olinska Institutet, Nobels Va ¨g 13, Box 210, S-171 77 Stockholm, Sweden. E-mail address: ulf.defaire@ki.se (U. de Faire). Contents lists available at ScienceDirect Journal of Autoimmunity journal homepage: www.elsevier.com/locate/jautimm 0896-8411/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaut.2009.05.003 Journal of Autoimmunity 34 (2010) 73–79