Abstract. Lundberg GA, Kellin A, Samnegård A, Lundman P, Tornvall P, Dimmeler S, Zeiher AM, Hamsten A, Hansson GK, Eriksson P (Ö rebro University, Ö rebro and Karolinska Institute, Stockholm, Sweden; and University of Frankfurt, Frankfurt, Germany). Severity of coronary artery stenosis is associated with a polymorphism in the CXCL16/SR-PSOX gene. J Intern Med 2005; 257: 415-422.Objective. Enhanced expression of CXCL16 has been demonstrated in atherosclerotic plaques and several properties have been attributed to CXCL16 that could influence the atherosclerotic process. CXCL16 exists in transmembrane and soluble forms. The transmembrane form acts as a scavenger receptor for oxidised LDL whereas the soluble form acts a chemoattractant for mainly CD8+ T cells. In addition, the soluble form of CXCL16 influences human aortic smooth muscle cell proliferation in vitro. In the present work, a human molecular genetic approach employing a common polymorphism within exon 4 of CXCL16 (181 Ala>Val) was used to investigate whether CXCL16 may be involved in the development of coronary artery disease. The polymorphism is located within the spacer region between the chemokine and transmembrane region and potentially influences an Ala/Val cleavage site, a site commonly used for the release of chemokines by tumour necrosis factora converting enzyme. Design and subjects. We first genotyped 387 unselected survivors of a first myocardial infarction aged <60 years and 387 sex-and agematched controls. A subset of patients (n ¼ 236) was evaluated by quantitative coronary angiography. Secondly, a cohort of 468 patients undergoing percutaneous transluminal coronary angioplasty (PTCA) with stent implantation was genotyped.Results. No significant difference in allele frequency between patient and controls of the 181 A>V polymorphism was detected. However, the V-allele was associated with increased severity of coronary stenoses. Secondly, the V-allele was associated with smaller minimal luminal diameter in the coronary segment subjected to intervention in a second cohort of patients undergoing PTCA with stent implantation. Conclusions. The present work provides evidence that CXCL16 is involved in processes leading to enhanced stenosis in atherosclerotic coronary arteries.