Abstract 2641: Natural Killer Cell Receptors Distribution In Patients With Carotid Atherosclerosis According To Clinical Expressivity
Background: Natural killer (NK) cells are lymphocytes involved in innate immune defence against viral infections whose function is controlled by a balance of inhibitory and activating NK receptors (NKR), shared by some T cell subsets. Healthy individuals infected with human cytomegalovirus (HCMV), a pathogen related to the development of atherosclerosis, display variable increased proportions of NK cells expressing the CD94/NKG2C activating receptor specific for HLA-E. On the other hand, some infections including HCMV may also increase the numbers of NK and T cells bearing LILRB1, an inhibitory receptor specific for HLA class I molecules expressed at late differentiation stages. LILRB1+ NK and T cells have been recently associated to acute myocardial infarction and carotid intima-media thickness, supporting the infectious burden hypothesis in the pathogenesis of atherosclerosis.
Objective: To evaluate NKR expression (NKG2C, NKG2A, LILRB1 and KIRs) in patients with carotid atherosclerosis according to their clinical expressivity seeking for a potential marker of high-risk carotid plaques.
Patients and methods: Peripheral blood was drawn from 30 patients with carotid stenosis higher than 50% classified as asymptomatic (n=11) and symptomatic (transient ischemic attack, n=10; acute ischemic stroke, n=9). HCMV serology and plasma levels of CRP were analysed in all patients. NKR expression by NK cells and CD8+ T lymphocytes were evaluated by immunofluorescence staining and flow cytometry analysis.
Results: Twenty-nine patients with carotid atherosclerosis were HCMV+. NKG2C expression by NK cells was similar in asymptomatic and symptomatic patients (17.6% ± 18.0 vs. 20 ± 19.2, p 0.7); moreover, both groups displayed as well a comparable distribution of other NKR, including LILRB1, by NK cells and CD8+ T lymphocytes. Yet, a positive correlation between the proportions of NKG2C+ NK cells and CRP plasma levels (Spearman correlation coefficient 0.5, p<0.05) was observed in symptomatic patients. In addition, LILRB1 expression by CD8+ T lymphocytes was directly related with age in the group of symptomatic patients (r 0.7, p<0.001) but not in asymptomatic patients (r 0.1, p=0.8).
Conclusion: Patients at increased risk of developing an acute stroke secondary to carotid atherosclerosis display an NKR expression pattern that might be linked to chronic inflammation; its putative relationship with the infectious burden hypothesis deserves further attention.
- © 2012 by American Heart Association, Inc.