Unstable Coronary Artery Plaque Features in Humans Are Associated with Higher Frequency of Circulating CD56bright Natural Killer Cells.

INTRODUCTION: Unstable human artery plaques can suddenly rupture, leading to MI or stroke. Identification of blood markers associated with unstable plaque features is clearly needed. Humans with symptomatic carotid atherosclerotic plaques have increased infiltration of CD56bright natural killer (NK) cells into the plaque, yet whether subjects with unstable coronary artery plaque features have increased frequencies of circulating CD56bright NK cells is unknown. METHODS: Coronary artery intravascular ultrasound (IVUS) was performed on subjects presenting for medically indicated coronary angiography. Eighteen subjects stratified into high and low percent (%) necrotic core and matched for age, body mass index (BMI), and lipids underwent mass cytometry by time-of-flight analysis on their peripheral blood mononuclear cells collected prior to imaging. Clustering of major immune cell populations was performed on live singlets and CD56 bright and dim NK subsets were quantitated. RESULTS: Subjects with high necrotic core had a significantly greater frequency of circulating CD56bright NK cells compared to subjects with low necrotic core (p = 0.02). Additionally, the frequency of circulating CD56bright NK cells positively associated with IVUS-VH metrics of total atheroma volume (p = 0.0013), percent (%) atheroma burden (p = 0.0048), % maximum stenosis (p = 0.0021), % necrotic (p = 0.0013), % calcium (p = 0.0016), % fatty (p = 0.0097) and negatively associated with % fibrous (p < 0.0001), an IVUS-VH metric of plaque stability. CONCLUSION: These findings suggest that the frequency of CD56bright NK cells may be a safe, noninvasive marker of plaque volume and instability.