Leucocyte-bound apolipoprotein B in the circulation is inversely associated with the presence of clinical and subclinical atherosclerosis.

Atherosclerosis is a pro-inflammatory condition, in which leucocyte activation plays an important role. The interaction between circulating leucocytes and apolipoprotein (apo) B-containing lipoproteins results in pro-inflammatory changes of these cells. We aimed to evaluate the relationship between apo B bound to circulating leucocytes and atherosclerosis. Apo B on circulating leucocytes was measured by flow cytometry in subjects with and without cardiovascular disease (CVD), expressed as mean fluorescent intensity in arbitrary units (au). Carotid intima-media thickness (cIMT) was measured using B-mode ultrasound. Data are given as median (interquartile range). A total of 396 subjects were included, of whom 183 had a history of CVD. Compared to subjects without CVD, patients with CVD had lower apo B bound to neutrophils (12·7 au (9·8-16·2) and 14·2 au (10·1-17·5), respectively, P = 0·038) and to monocytes (2·5 au (1·7-3·1) and 2·7 (1·9-3·6) au, respectively, P = 0·025). No differences were found for lymphocyte-bound apo B. Neutrophil- and monocyte-bound apo B were inversely correlated with cIMT (Spearman's rho: -0·123, P = 0·017 and -0·108, P = 0·035, respectively). Both monocyte- and neutrophil-bound apo B were inversely associated with different factors related to the metabolic syndrome, such as body mass index, triglycerides and complement C3. There was a positive association between erythrocyte-bound apo B and apo B bound to each of the leucocyte classes, possibly reflecting a similar mechanism. Discontinuation of statins in 54 subjects did not influence leucocyte-bound apo B. Unexpectedly, the presence of noninternalized apo B-containing lipoproteins on circulating neutrophil and monocyte membranes may represent a protective mechanism against atherosclerosis.