Circulatory markers of immunity and carotid atherosclerotic plaque

Background and aims: We aimed to determine the association of circulatory markers of innate and adaptive immunity with carotid atherosclerotic plaque characteristics.

Methods: In 1602 participants from the population-based Rotterdam Study with subclinicalcarotid atherosclerosis, blood sampling was performed to determine granulocyte, platelet, monocyte (innate immunity) and lymphocyte (adaptive immunity) counts, from which the granulocyte-to-lymphocyte ratio [GLR], platelet-to-lymphocyte ratio [PLR], monocyte-to-lymphocyte ratio [MLR] and systemic immune-inflammation index [SII] were calculated. All participants underwent carotid MRI for evaluation of plaque characteristics. Plaque size (stenosis >30%, maximum plaque thickness) and plaque composition (presence of intraplaque hemorrhage [IPH], lipid-rich necrotic core [LRNC], and calcification) were assessed. Using linear and logistic regression models, the association of innate and adaptive immunity markers with plaque size and plaque components, adjusting for relevant confounders, was assessed.

Results: Higher levels of granulocytes were significantly associated with larger plaque thickness (mean difference [Ln (mm)] per Ln increase granulocyte count [95% CI]: 0.06 [0.02; 0.10]). Conversely, more lymphocytes related with smaller maximum plaque thickness (mean difference [Ln (mm)] per Ln increase lymphocyte count: 0.09 [-0.14;-0.04]) and a lower prevalence of IPH (odds ratio per Ln increase lymphocyte count: 0.60 [0.37; 0.97]). Moreover, all ratio measures were associated with larger plaque thickness, of which the MLR also associated with more frequent LRNC (odds ratio per Ln increase MLR: 1.26 [1.02; 1.56]).

Conclusions: The innate immunity links to larger plaques, whilst the adaptive immunity seems to relate to smaller plaques and a lower frequency of IPH. These results suggest that an imbalance in innate and adaptive immunity may play a role in the vulnerability of carotid atherosclerotic plaques.